Scrolling through social media in September and October and you may see those basic signs of the season: scarves, pumpkin spice lattes, sweaters, and Halloween ideas galore. One of those Halloween ideas is to extend the life of your pumpkins, carved or otherwise, by giving them a treatment with household bleach. Keep scrolling and you might see another post decrying the use of bleach as inhumane and poisoning for wildlife. So which is it? Is bleach safe to use as a sanitizer on your jack-o’-lantern or are you poisoning the neighborhood squirrels? Let’s use our gourd to explore the science.
The bleach acts as a sanitizer, neutralizing fungi and bacteria on the surfaces of the pumpkin that will cause decomposition and rot. Even un-carved pumpkins will eventually succumb to degradation under the right conditions. But if bleach kills fungi and bacteria, will it kill wildlife? The answer is – not if it is used correctly. Bleach, and sodium hypochlorite (the active chemical in bleach) are toxic if consumed directly in concentrated amounts, however, dilute solutions break down quickly in the environment. Products containing sodium hypochlorite, including plain household bleach, are actually approved and labeled for use as a sanitizer by produce farmers to reduce both human pathogens and decomposition microorganisms and extend the shelf life of produce that finds its way to the grocery store, farmers market, and any other avenue from the farmer to the consumer. These wash water sanitizers are used more for reducing cross contamination of from pathogens introduced to the water from dirty produce, but it can reduce the microorganism load on produce items. If used correctly to sanitize the surface of the pumpkins, bleach DOES NOT pose an increased risk to wildlife (or human) health.
What is the proper way to use bleach in sanitizing that pumpkin so that it doesn’t face an early demise?
1) Make sure the
pumpkin is clean by washing with plain water or a mild detergent to remove any
soil or debris. Sanitizers like bleach
are quickly neutralized (used up) on dirty surfaces (this is a good lesson for
home cleaning, too – you cannot sanitize a dirty surface).
2) Prepare a DILUTE solution of plain household bleach (unscented, and not “splashless”). The recommended concentration is 200ppm sodium hypochlorite, which you can achieve with 1 Tablespoon of bleach per gallon of water.
3) Apply the solution to the pumpkin using a spray bottle. Alternatively, you can prepare enough solution to dunk the pumpkin(s) and immerse them in the solution. If you are sanitizing a carved pumpkin, I would opt for the spray method – dunking may result in infiltration of the solution in to the exposed flesh. It will still break down since it is a dilute solution, but it will slow down the process since it protects the bleach atoms from air and sun exposure.
4) Allow the pumpkin to air dry. Sanitation is not immediate (keep that in
mind for sanitizing surfaces in the home, as well) and wiping can cause cross
contamination
If I can do this with a pumpkin, should I be doing this with my other produce?
The short answer is NO.
It is not recommended that home grown or purchased produce be washed
with any sort of detergent or chemical in the water. Fresh cold water and friction should be sufficient
for removing soil and pathogens on the surface.
Proper protocols, equipment, and training are needed to make sure
sanitation is done properly. Knowing which produce items can and cannot be
washed with a sanitizer is important. However, if you are harvesting produce
like pumpkins or winter squash for long-term storage you may want to consider
sanitation using the above methods.
I don’t want to use bleach, can I use something like vinegar?
There are many sanitizers approved for use by produce growers for sanitation, so bleach is not the only option. For home consumers there aren’t so many options. Vinegar is often mentioned as a wash for produce. I found no direct mention in produce handling guides of using vinegar on pumpkin, but most produce wash solutions use vinegar at a much higher concentration because it is much less effective at sanitation. I found rates ranging from 1/3 c vinegar to 1 c water to 100% undiluted household vinegar for use as a produce wash.
As summer winds down and the summer crops and flowers start
to slow down many gardeners start thinking about saving seeds. Who doesn’t love
saving seeds from that favorite tomato or beautiful coneflower? Not only do you have some for next year, but
you can also share with your friends! There are definitely some things to
consider and some myths out there when it comes to seed saving, so let’s talk
about how to do it right.
You’ll get the most consistent results from open pollinated or heirloom varieties that are self-pollinating. These plants have genetics stable enough that the seeds you save will come out looking and acting like a close approximation to the plants from the previous season (with some variation based on your selection of the “best” plants you save seeds from. Self-pollinating species are: tomatoes, peppers, eggplant, beans, peas, peanuts (note, peppers and eggplants have more open floral structures that can be cross pollinated). Most tree fruits like apples and pears are cross pollinated and they are notorious for not “breeding true” – even if you hand pollinate to ensure that the mother and father are both the same cultivar you’re likely to get surprises. Stone fruits (peaches, plums, etc) are less variable but still not true-breeding. Bee pollinated plants are also notoriously hard to save seed from, since they can cross pollinate with different varieties and cultivars from miles away. It is especially interesting for plants that look totally different but are the same species (like pumpkin and zucchini).
A puccini or a zumpkin? Either way, it tasted nasty.
Myth: You can’t save seeds from those new modified hybrid plants. They’ve been made to be sterile
First off, hybrids aren’t genetically engineered and there are no GE plants available to home gardeners (most home garden crops don’t even have GE versions). Hybrid plants do in fact usually produce viable seeds. However, you won’t get the consistent results you will with open pollinated/hybrid varieties. Hybrids are the F1 generation of a specific cross between a mother and father plant. The offspring from that F1 generation (the plants from the seeds you save) is called the F2 generation will be a mix of traits – some will look like the F1 generation, some will look like the mother, some the father, and some the milkman. So you’ll be in for a mixed bag of surprises. According to our former GP colleague Joseph Tychonievich’s book “Plant Breeding for Home Gardeners” you can even develop a stable open pollinated variety from hybrids by saving seeds over a few seasons, selecting seeds from the plants that most resemble the cultivar you’re trying to save.
You’ll want to make sure that the fruit/flower head that
you’re saving seed from is mature. This
can be tricky for some vegetables, because we eat them in their immature
states. Peppers need to change from
green to whatever their color is (red, yellow, orange, purple, etc), cucumbers and zucchini (and other squash)
need to turn into those massive, bloated fruits that often change to yellow or
orange. Beans often need to change to
yellow or tan (and may have stripes).
For flowers, the seed heads or fruiting structures often need to turn
brown and dry or start to open.
If the weather cooperates, you’ll want to collect seeds from
dry fruits/structured (beans, some flowers, etc) before significant rainfall so
that seeds don’t become wet and potentially mold or break dormancy. Collect seeds and place in a warm, dry
location to let them continue drying out (if they’re small you want to put them
somewhere they won’t blow away). After
drying, store seeds in envelopes or containers and put them in a cool dry
place. I often tell people to store
seeds in the freezer – the cold temperature slows down respiration in the seeds
and can extend their lifespan (the fridge is too moist/humid). If you do that, drop your envelopes or
containers down into a sealable container or bag to help keep condensation
minimal when you pull them out of the freezer next year.
For home gardeners, it may not matter that you get plants
next year that exactly copy the ones you saved seeds from – the fun can be in
the surprise. Who knows, you may
discover a new variety – at least one that is exciting to you. It can be fun seeing the variation in your
new plants and finding something that you love.
Epilogue: A special case – tomatoes
Most of the vegetable crops we grow don’t need any special treatment to break their dormancy (you’ll have to research flowers on a case-by-case basis) – save the seed and plant it next year and it will pop up. Tomatoes are a bit of a special case. If you scrape the seeds out of the fruit you’ll notice they’re still covered with the “goo” from inside the tomato which is called interlocular fluid (interlocular = between seeds). The coating persists on the seed even if you wash them. It has long been held that this coating retains some of the hormones of the fruit (like abscisic acid) that inhibits germination (though not all experts agree). So many sources will tell you to go through some process to break down the coating left on the seed, most commonly by placing the seeds and associated goo in a container, adding a bit of water, and letting them ferment for a few days. You can dump them out and wash off all the gunk. Whether or not this is required to break dormancy is up for debate, but it does provide you with clean seeds that you can store easily. There is also some evidence to suggest that this fermentation process helps remove pathogens on the exterior of the seed (heat treatment can help remove interior pathogens as well).
Some people just scoop out the seeds and smear the goo on a
paper towel and try to scrape them off next year. Some people add the step of washing, but this
will still not remove all of the goo coating the seeds. This works if you’re
not trying to share (or sell seeds) since they will stick to the paper towel. My
guess is that the in the day or so that it takes for the goo to dry there is
enough fermentation or decomposition going on to break dormancy. If you don’t want the seeds stuck to a paper
towel, you can use wax paper or some other non-binding surface, but you’ll
still have dried goo on your seeds.
Ah, summer – vacations (pre-COVID), swimming pools
(pre-COVID), ice cream, vegetable gardens, and, in many places, really high
temperatures. These things all go
hand-in-hand (or at least they did before the pandemic). Many gardeners feel
that the heat of mid-summer goes hand in hand with garden production; those
high temps driving production on those fruiting plants like tomatoes and
peppers. But…..could they be wrong?
We’ve had lots of extra hot days this summer in Nebraska, so it stands to reason that we should have really great production on those garden favorites like tomatoes, right? Then tell me why our extension office has received numerous questions this year about why tomatoes aren’t setting on or ripening. Heck, we even had a Facebook post about tomatoes not ripening in the heat go viral (well, for our standards – 300,000 views/2,000 shares). Could it be a disease? Nope – it’s the heat. High daytime temperatures can have a big effect, but the effects are compounded when nighttime temperatures are high as well.
Tomatoes not ripening? You're not alone. Temperatures above 85 degrees will slow down the ripening process. Temperatures above 95 can stop the process all together. #NebExt #NeWX
It turns out that high heat does two things in many of those
fruiting vegetables (and of course fruits) that we grow. First, it inhibits pollen production, which
in turns reduces fruit set. Second, heat
inhibits gene expression for proteins that aid in ripening/maturation of the
fruit. Heat stress also reduces
photosynthesis (Sharkey, 2005) in many different plants, which would slow down
plant processes (such as fruit development and ripening) as it reduces the
availability of sugars to fuel these processes.
So high heat can not only reduce the number of fruits developing on the
plant, but also slow down the ripening process for fruits that have already
set. And if you think that these effects
only happen at super extreme temps, most of the research studying temperature
effects of this nature use a common “high ambient temperature” of 32°C/26°C
for daytime/nighttime temperatures. For us U.S. Fahrenheit-ers, that’s 89.6°F/78.8°F,
which isn’t really all that hot for most of us.
Many studies show that application of this “high ambient
temperature” to crops such as tomatoes, beans, and corn during the
pre-fertilization phases of reproduction (ie – flower/pollen development) can
negatively effect fruit set. The
introduction of Porch and Jahn (2001) gives a pretty good overview of
literature detailing the effect in beans (Phaseolus vulgaris). I’ll sum it up here: heat stress while the
pollen is forming (called sporogenesis) led to pollen sterility and failure of
pollen to release from the anthers (dehiscence). It also led to flower abscission (basically
the plant aborts the flower) and reduce pollen tube formation (how the pollen
nucleus gets through the stigma to the ovule for pollination) when applied
during the period of pollen sac and ovary development. And application during flower opening
(anthesis) resulted in pollen injury (sterility) and reproductive organ
abscission. All of these effects lead to
reduced fruit/seed set in beans. (Interestingly,
heat stress at the ovary development phase also led to parthenocarpy –
basically the pods developed, sans seeds, without fertilization).
However, we get the most calls about tomatoes (they’re the top crop for most home gardeners). Is it the same issue? Yep. Numerous studies (Sato, et al., 2000; Pressman, et al., 2002; Abdul-BAki, 1992) show the same effect in tomatoes. Pressman, et al. (2002) linked the effects on pollen to changes in carbohydrates in the anthers (reduced starch storage and carbohydrate metabolism).
Tomato floral structures
To add insult to injury, high temperatures also slow down or stop ripening of crops like tomatoes. Picton and Grierson (1988) found that 35°C (95°F) temperatures altered the gene expression in tomato fruits – inhibiting the expression of polygalacturonase, which softens cells walls, allowing the fruit to ripen. Reduced photosynthesis would also reduce the availability of sugars for fruit development and ripening.
But there’s hope, both this season and in the long term! The effect on the plants is not permanent. When temperatures drop below that “high ambient temperature” threshold pollen production, and therefore fruit set, will return to normal (as long as the plant is healthy). Sato, et al. (2000) found that pollen release and fruit set resumed within a few days after heat stressed plants were “relieved” and temperatures dropped back into the optimal range of 26-28°C/22°C (78.8-82.4°F/71.6°F). So many of those plants will become productive again (good news for my own tomatoes and beans, which had an initial flurry of production then went on vacation), especially as we head into fall. And efforts are under way to develop and test heat stress resistant cultivars.
This last point may be more important than you realized. These production problems plague many areas
around he world at current climactic norms.
Many fear that increasing temperatures will limit the productive
capacity of many areas of the world that are already struggling. It is easy to see how the difference in just
of just a few degrees can take your veggie production from prolific to paltry.
You can also try to reduce the heat a bit yourself for an immediate fix. Shade cloth can help reduce temperatures a little bit, which may make all the difference in your garden if you’re just slightly over the “high ambient temperature” threshold.
Tomatoes under shade cloth | Source: flickr.com
But in the meantime, if your vegetable garden has taken a summer siesta it will get around to producing again one day. You’ll just have to take good care of the plants in the meantime. And perhaps it’s a blessing in disguise – when its that hot I don’t want to be out working in the garden much, either.
Sources
Abdul-Baki, A. A. (1992). Determination of pollen viability in tomatoes. Journal of the American Society for Horticultural Science, 117(3), 473-476.Porch, T.G. and Jahn, M. (2001), Effects of high‐temperature stress on microsporogenesis in heat‐sensitive and heat‐tolerant genotypes of Phaseolus vulgaris . Plant, Cell & Environment, 24: 723-731. doi:10.1046/j.1365-3040.2001.00716.x
Pressman, E., Peet, M. M., & Pharr, D. M. (2002). The effect of heat stress on tomato pollen characteristics is associated with changes in carbohydrate concentration in the developing anthers. Annals of Botany, 90(5), 631-636.
Sato, S., Peet, M. M., & Thomas, J. F. (2000). Physiological factors limit fruit set of tomato (Lycopersicon esculentum Mill.) under chronic, mild heat stress. Plant, Cell & Environment, 23(7), 719-726.
Sharkey, T. D. (2005). Effects of moderate heat stress on photosynthesis: importance of thylakoid reactions, rubisco deactivation, reactive oxygen species, and thermotolerance provided by isoprene. Plant, Cell & Environment, 28(3), 269-277.
While most of the country is in the
middle of a heat wave and the mercury is creeping past 100F on many
thermometers, lets do a little exercise to help you feel cool as a cucumber
(though not straight out of the garden, those cucumbers would likely be hot). I want you to think about a crisp September
morning. You’re out walking through your
vegetable garden and you stop to appreciate a big, emerald green head of
broccoli. Just a few feet away, stalks
of Brussels sprouts, those miniscule cabbages that have somehow overcome years
of revulsion to become sexy and desirable (they must have a good agent) shoot
up like skyscrapers around the rest of the plants. Lush lettuce fills in a bed nearby, and some
cucumbers and beans that you planted late are looking as fresh as a newborn
chick.
Sounds beautiful, doesn’t it? Well I’m here to tell you that you can
actually make this a reality. You can
have a super productive garden this fall, and for most areas of the country the
time to start planning and planting is now.
Right now, when a cool refreshing fall morning seems as far away as a
trip to the moon. Of course, the exact
timelines and planting schedules differ by region due to the length of growing
season, but most places in the US (and the northern hemisphere) can start
thinking now about planting crops for the fall.
For exact timing in your area, you may want to connect with your local
extension system for gardening guides.
While many experienced gardeners may
know this and practice fall garden planting, there’s a lot of people out there
who have yet to have the pleasure. And
given the huge number of first time (or first time in a long time) gardeners,
these garden basics might be helpful to get the most out of those pandemic
plantings.
In fact, fall is one of the best times of the year to garden. Aside from cooler temperatures making it more pleasant to garden, there’s often less pressure from diseases and insects to ruin crops. In addition, many of those cool season crops, like the ones I mentioned above, actually are more productive in the fall than if planted in the spring. Even though they get a hot start in mid- to late- summer, the cooling temperatures of fall around the time many of the crops come into maturity extends the harvest period and improves overall quality of the produce. You also have the benefit of removing some of those spent and diseased warm season plants and swapping them out for something fresh and new– a garden revival of sorts.
Swiss chard and leafy greens are great additions to the fall garden
Unfortunately, since fall vegetable gardening isn’t as widespread as planting summer gardens, plants and seeds can often be hard to find when it is actually time to plant (so planning ahead is helpful). Mid-summer is usually the time for most regions to start seeds for those slower growing cool season crops like broccoli, cabbage, cauliflower, and their kin. They can be started indoors, but the need to do so isn’t as great as it is for those warm season crops we start indoors in late winter. You can start them in pots/flats outdoors as long as you have somewhere that isn’t so hot and sunny that they’ll be continually drying out (some shade would help). They should be ready to transplant by late summer. You can skip the seed starting/transplanting if you want to try direct seeding into the garden, but as they say “your mileage may vary”.
Some of the fast maturing warm season (frost tender) crops are
also good candidates for a mid-summer planting as a way to refresh the garden
if you have space for it. Beans are a
good candidate for late-summer planting, but you’ll need to make sure they are
a fast-maturing variety (there’s a wide range of maturity times in beans). Bush
beans are usually the quicker growers. Pole beans and lima beans usually take a
longer period, so those don’t do as well later in the season for places that
have frost and freezes.
It is also a possibility to squeeze in a late crop of cucumbers
or summer squash as well. This can be good if your cukes and squash succumb to
disease, squash vine borers or cucumber beetles. Planting late can often mean
that you are missing the primetime for specific pests. For example, squash vine
borer adults actively lay eggs in the early season but largely disappear later
on. A late planting means you could miss
them entirely.
Fall is the best time to grow leafy green vegetables.
Lettuce, which does not fare well in the summer, thrives in the cooling
temperatures of the fall. Other leafy greens, such as chard, spinach, and
kale are also winners in the fall garden.
Many of the root vegetables, such as turnips, carrots, beets, and
radishes are also part of the fall garden revival. You’ll want to wait
until temperatures have chilled a little to get these started, but not so late
that the season ends before you get good growth.
You gotta know when to sow ‘em
The key to fall planting is to know how many days it takes for
the crop to mature. Check out the seed package or the plant tag — there should
be a time to maturity on there. Just count backward from the first frost date.
Be sure to add a few weeks to account for slower growing in cool weather and to
allow for a reasonable harvest time.
For example, if I wanted to plant a late crop of beans, I might
select the cultivar ‘Contender’ which matures in about 55 days. I want to add at least a few weeks onto that
for maturity and harvest time, so lets say I need 75 days (I can go shorter if
I want to accept the risk of an early frost).
Let’s also say that my first frost date in the fall is October 20. Counting back 75 days from October 20, I get
August 6 – I should plant my beans no later than that date to get a harvest.
Most of the cool season crops can tolerate a frost (and some even a freeze) so their growth dates can extend beyond the first frost date. You’ll just want to have them mostly grown and close to maturity before it gets cold enough to stop their growth. I covered frost and freezes and which crops can survive those cold temps in this previous GP article.
You can give yourself a little more time if you plan on
incorporating a season extension practice in the garden. Using a row cover or
constructing a low tunnel can give you several more weeks of growing time. It
can be possible to enjoy a fresh tomato or green beans straight from the garden
on the Thanksgiving table, or some fresh broccoli or kale at Christmas even in
some of our colder regions. But it all starts with a little planning in the
heat of summer.
And if you choose not to plant a fall crop, I would suggest using a cover crop in garden beds as you remove this year’s plants. A cover crop will help keep weeds to a minimum and preserve soil structure and nutrients through the winter. Winter wheat, rye, and crimson clover are good winter cover crops. Next spring you just cut them down and till them in if you’re not practicing no-till (and you should be if at all possible). For annual cover crops, you can usually cut them down or break them over and leave them in place as a mulch. You can also pull them up and compost them to add directly back to the garden, especially if (since it is hard to till or mow in a raised bed). This GP article is an oldie but goodie for using cover crops in the vegetable garden.
While we can’t ever
control or even predict the weather, in most places it is important to have a
plan on how to deliver water to our home gardens during the hot, dry months of
the summer. Aside from reducing water
need through some good management practices, delivering water in an efficient
and sustainable way is important when planning and planting our home
gardens.
When there is
scarcity, it is necessary to conserve. Several years I got to see scarcity in
person on a sustainable agriculture tour of New Mexico. Farmers in New Mexico have only limited
access to water from irrigation canals, to flood irrigate their fields, or even
wells for drip irrigation.
This severe lack of
water got me thinking about how much we take water for granted in our own
gardens. We often apply as much as we
want or need in an inefficient manner (using sprinklers, sprayers, etc.)
because we think it will always be there when we turn on the tap.
Where I’m located in
Nebraska we are also blessed to have water falling from the sky. Sometimes
there’s too much, and at others there’s not enough. But that’s much better than
in some places – I visited some parts of New Mexico on a farm tour where they
get seven inches of rainfall in a normal year. Seven. Total.
Thinking about
conserving what water we have means that we are good stewards and are ready for
when issues do arise. And let’s face it, there are some times in the summer
that are dry where water conservation will help reduce using water, which can
also save money.
When we talk about
conserving water, there are two ways to go about it. First, look for ways to
reduce the need for water. Then, look at ways to reduce water waste and usage
whenever you need to use water on your lawn, landscape or garden.
Reducing the need for
water
During dry times, it
can be necessary to provide water to the garden to keep it growing healthfully
along. However, there are many ways to reduce water loss or increase the amount
that stays in the soil around the plants.
Mulching not only
reduces weeds, but also helps hold moisture in the soil. Having one to two
inches of mulch on landscape beds can reduce evaporation from the soil and
decrease the amount of water you need. Newly planted trees should be mulched
for the first few years to help hold moisture in the root zone as well.
Mulching is also important in the vegetable garden. Using straw or shredded newspaper are simple ways to conserve moisture, beat weeds and even reduce diseases. Note that this is shredded newspaper used on top of the soil for a mulch, not whole sheets applied below another mulch or on top of the ground. That process is called “sheet mulching” and we typically don’t recommend it here at the GPs because it limits air movement into the soil and can disrupt the soil microbiome. Stick only to shredded newspaper as a top dressing. (See the bottom of the article for journal articles discussing paper and straw mulches).
Shredded newspaper in my tomato bed. There are 2ft woodchip mulch walkways between 4ft wide beds.
You can use woodchip
mulch in the vegetable garden, but it can be difficult to manage when you are
frequently planting, replanting, or harvesting crops. If you accidentally incorporate it into the
soil, it can tie up nitrogen available to plants and cause deficiencies. As long as you are good at keeping it on the
surface, it isn’t as much of an issue.
Large scale gardens or
farms make use of black plastic as mulches to do much the same thing. Plastic mulches
are typically beyond the scale needed for home vegetable gardens and have their
own set of drawbacks such as limiting water and air movement, but for those struggling
with difficult weeds or with issues limiting manual removal (disability,
limited movement, etc) it may be explored for smaller scale production. There
are now even biodegradable plastic and paper mulches available. Use of these
does require drip irrigation beneath the mulch, as rain cannot penetrate to the
root zone. With the issues associated with them, plastic mulches would be
considered a last resort for all but the largest home vegetable gardens, and
many of my GP colleagues recommend against them for all home garden situations –
but they can have their very limited place in the home garden toolbox. And we definitely recommend against the use
of plastics and landscape fabrics in ornamental beds and landscapes.
Choose plants that
require less water. There are many plants available that have lower water
requirements. Ornamental grasses, Liatris (blazing star), Kniphofia (red hot
poker) and sunflowers come to mind. Most native plants are commonly thought to
have lower water requirements, but this isn’t always the case and natives may
not thrive in altered ecosystems (urban settings or even managed landscapes).
Most bulbs also are water efficient and do not require extra watering, as are
most culinary herbs.
Mowing less often in
the hot and dry summer also can conserve water if you are one who waters the
lawn. I’m not a big fan of watering lawns, since it is such a large water usage,
but I know there are those who prefer to have their lawns lush and green at all
times. Instead, when the summer gets hot and dry, leaving the grass on the
taller side can help it stay green even without water. Many of the grasses we
grow here are cool-season and go semi-dormant in the heat. Stopping mowing when
the heat starts slows down growth and the need for water.
Irrigating Efficiently
with Drip
When it comes to
getting water to the garden, there are definitely more efficient ways to make
it happen.
Unfortunately, the
most common method — using sprinklers — is also the least efficient. It is hard
to direct the water to the right place, and during periods of high heat
evaporation takes up much more water than you think. But there are ways to get
water to your thirsty plants without running up the water bill.
Drip irrigation is probably
amongst the most efficient and sustainable ways to water your landscape or
vegetable garden. This method allows you to apply water directly to plants in a
controlled manner, rather than spraying an entire area with water. Also, since the water is applied directly to
the ground rather than sprayed through the hot summer air, the water is much
less likely to evaporate.
Drip irrigation tubing. Each drip opening emits on this version emits 1 gallon of water per hour.
There are a few
different types of drip irrigation systems available. Probably the easiest to install is a drip
tape system. This is a deflated tape
that already has water-emitting slits cut into it. While each slit applies a precise amount of
water over a given time period, the pre-determined regular placement of the
slits makes this system better for plants grown in rows, like vegetables,
rather than landscapes where plants are of differing sizes and spacing. And while it can be used for vegetable gardens,
probably the easiest system for a landscape would be one where there are tubes
you can cut to various lengths and insert controlled drip emitters at
customized locations. Another use for
this type of drip irrigation could be for containers on a porch or deck – you
can easily run the tubing out of sight along a bannister or railing and direct
individual emitters to individual containers.
It all sounds
complicated, and larger systems can be, but there are small and simple kits you
can easily find at many garden centers or online retailers available for home
gardeners to install their own within a matter of hours. You will need to have
some skill at reading directions to install them, but the process is pretty
simple.
For information on
setting up drip irrigation for your home garden, check out these great
resources from Extension institutions across the country:
Soaker hoses are a
similar concept to drip irrigation, but instead of small drips these hoses just
emit water all along the hose. Still better than sprinklers, these hoses are
quite a bit less efficient than drip, since you can’t direct the water exactly
where you want it. They are also easy to
apply too-much water to an area since they can emit large volumes. Installation
is pretty simple, though, since you just lay the hose down where you want it.
One great benefit of both drip irrigation and soaker hoses is the application of automation. Using a timer can make it easy to keep the garden watered through the season. Timers can be as simple as a dial to manually run the irrigation for a specified time or fully automatic to run the irrigation for various lengths of time on different days of the week. Some more advanced timers also have rain sensors or soil probes to reduce or avoid running when rain makes watering unnecessary (if you don’t have a sensor, remember to stop automatic running until the soil has dried). And in today’s emerging technology, there are also timers or flow controls that can be automated or controlled from a phone app. The timer that I’m now using at home connects to my Wi-fi, and in addition to allowing me to control and observe the watering status from anywhere in the world, connects to local weather data to automatically set a “smart watering” schedule taking into account rainfall, temperature, wind speed, and other factors.
My fancy water timer.
Another effective way
of providing water to your garden is through water catchment. Water catchment is just a fancy way of saying
that you use a rain barrel. Here you are collecting rain runoff to use in place
of water from the tap. There are some ultra-low-flow drip irrigation systems
that you can use with rain barrels (if they are raised high enough to get water
pressure), but this use is usually for watering by hand. For larger gardens,
the large IBC totes that hold 200 or more gallons can make good water catchment
barrels. Just make sure that if you are
using them (or any other barrel) for fruit or vegetable production that they
are made of food-safe plastic and their previous contents were also food safe. (Check out our guide on Building a Rain Barrel)
Now that much of the world’s attention is focused on
limiting the spread of pathogens, well one pathogen, it seems like a good time
to talk about some of the questions or concerns we’ve seen regarding vegetable
gardens, community gardens, and farmers markets. It’s a good time to talk about some of the
practices that we should be doing to prevent other human pathogens from
handling produce, like E. coli and Salmonella, and how those might fit into
preventing the spread of COVID-19.
First things first
First off, we have to remember that SARS-CoV-2, which is the virus that causes COVID-19, is not a food borne illness. I repeat: COVID-19 IS NOT A FOOD BORNE ILLNESS. This means that it is not spread through the consumption of contaminated food like E. coli and Salmonella. I’ve seen many instances of people spreading fear about food online, with many suggesting using soap or bleach on food to minimize risk. Those steps are both unnecessary an actually pose a poisoning risk. There is currently no evidence to suggest that COVID-19 is transmittable by food or food packaging.
The risk from food (which is considered minimal by experts)
is from cross-contamination from food or packaging onto hands or onto surfaces
that are then touched by hands. The
virus would then have to go from a persons hand to mucous membranes in the
respiratory system by something like touching your face or picking your…..well,
we won’t go there. The best defense
against this isn’t necessarily sanitizing all the food you buy, but washing
your hands after you handle it and sanitizing any surfaces that packaging or
shopping bags touch.
But while we’re on the topic of pathogens and food safety,
it’s a good time to talk about some general guidelines that can not only help
stop that potential SARS-CoV-2 cross contamination but also food borne illness
in general.
Minimizing the risk from produce even further
Whether you grow it in your own garden, buy it at a local
farmers market, or purchase it at the grocery store, produce has a minimal risk
when it comes to COVID-19.
To minimize the very small risk of cross-contamination even further and (probably more importantly) to also reduce any risk from common food borne illnesses, proper washing of the produce should be practiced. But do you know how to do that? Maybe…and maybe not. Here are some steps to help out.
Wash your hands. The most common pathway of contamination for produce is from human touch.
You should use clean water that you would use for drinking (like out of the tap) and not use any bleach or soap.
Providing gentle friction with your hands or a produce brush or by rubbing the produce together is sufficient.
If you’re washing a lot of produce at once, say from a large harvest, and you’re using a tub full or sink full of water to wash multiple “loads” of produce, keep an eye on how dirty the water gets and refresh it when it gets discolored. Remember that washing produce in a tub or sink of water can also present a cross-contamination issue where contaminated produce contaminates the water.
When in doubt, discard produce you may think is contaminated or wash it separately.
To reduce risk of cross-contamination, consider a “single pass” washing technique where you spray the produce with water and it doesn’t sit in water with other produce.
Food Safety in the Garden
There are a few things we can do in the garden to help stop
the spread of human pathogens. Most of
them are common sense things that most people don’t even think about. Devout GP readers may remember my little
missive around this time last year about the food safety risks of using manure
in the vegetable garden (See: The
Scoop on Poop). Beyond those musings
on manure, though, gardeners can take some additional steps to reduce potential
contamination. Those are:
Wash your hands.
I know it sounds simple, and maybe even more so now that it has been
drilled into our brains, but washing your hands before you garden is one of the
best ways to reduce the spread of pathogens.
It is especially important to wash your hands before you harvest produce
or handle harvested produce.
Use clean containers for collecting and storing
produce. Using harvest baskets, tubs,
and totes is common, but the ones that are best in terms of food safety are
those that can be washed and sanitized.
This is one tactic that many farmers are encouraged to use as well. Plastic tubs, totes, trugs, and crates are
probably best as they can withstand washing and the use of a sanitizer like
bleach. Wooden or woven baskets may be
cute, but they’re harder to clean and can hold on to pathogens.
Look for signs of wildlife in the garden. Aside from eating more than their fair share
of produce, wild animals can also present a food safety risk especially from
their droppings. Look for signs of
animals in the garden and especially take note of any droppings. Don’t harvest produce that has signs of
droppings on them. Many of the big
produce recalls over the last decade have been a result of wild animals like
birds or wild hogs.
Keep pets out of the garden. As much as you like to have Fluffy or Fido in
the garden, they present a risk just like wild animals do.
Wash produce using proper techniques (previously
discussed).
Best practices for minimizing COVID-19 risks at Community
Gardens (and Farmers Markets)
One other aspect of gardening that could provide some risks for the spread of COVID-19 are the more social aspects of gardening, such as community gardens. I’ve had several local gardens reach out for best practices relating to minimizing risks in the garden – from handwashing stations to shared tool use. Thankfully, NCSU Extension was quick on the draw with resources for lots of aspects of the food system in terms of reducing risks from COVID-19 and they graciously allowed other universities to distribute these resources. Below are some links to the resources that would be helpful to gardeners:
Except for areas of the US that are more tropical like southern Florida or Hawai’i, most gardener’s planting schedules are set around winter weather and the possibility of frost or freeze. And even for gardeners in those more tropical areas, planting sometimes needs to be planned to schedule around the extreme heat of summer. Understanding these planting times can really lead to success or failure, especially for vegetable gardens, tender annuals, tropicals, and non-dormant perennials. There are a few tools that help us understand weather patterns and predict critical temperatures for planting, namely the USDA Hardiness Zone map and the Average Last Frost/Freeze dates. The USDA Hardiness Map shares data on what the average coldest temperature is, which is key for selecting perennial plants that you want to survive the winter. However, to know when to plant we look at the average freeze and frost dates. There seems to be a little bit of mystery, and even confusion, around the dates and how to interpret them, so let’s take a little time to understand them a little better. And since my background is in vegetable production, I’ll share a bit more detail there in terms of plants – but you can translate the information to ornamentals, especially those that are frost tender pretty easily.
Understanding Average Last Frost Date
What is the average last frost date and how is it figured? The average last frost date is exactly what it says it is – the average date at which the probability of frost has diminished. Just how diminished really depends on the source, so we’ll follow up with that in a bit. The data is computed by NOAA (National Oceanographic and Atmospheric Administration) and the National Weather Service to determine the probability of temperatures relating to frost and freezes based on weather data for an area over the last 30 years. They compute the likelihood of a light frost (36 F), frost/heavy frost (32 F), or freeze (28 F) at three different probability levels – 90% (the temperature is very likely to happen), 50% (the possibility is 50/50), or 10% (the temperature is unlikely). This tool from NOAA provides a chart with probabilities for locations throughout each state.
This data is typically collected and analyzed every ten years or so. I’m not exactly sure when the last data was analyzed, but I did find some maps on the NWS referencing the period 1980/81- 2009/20 (below). Therefore it is likely that new data will be released either this year or next year.
Temperature hardiness of common vegetables
Awareness of tolerance is especially important for vegetable crops, as the growing season and expected productivity of the plants. The following chart is a general guideline, and your mileage may vary based on cultivar difference, microclimates, and other factors. Also note that these temperatures are for both planting in spring and fall kill temperatures. Some of the more tender plants, like tomatoes, may withstand colder temperatures when they’re mature so they may be less susceptible to frost at the end of the season vs. the beginning of the season.
Season extension techniques, such as row covers can be used
to protect tender plants in the spring and extend harvests in the fall. Row covers can be selected by the degrees of
protection they deliver. For example, a
row cover may offer 4 degrees of protection.
This allows the protected plant to withstand air temperatures 4 degrees
colder that what it would unaided. For fall crops, note that plants may stop
growing well before the kill temperature but will hang out in “stasis” until
they are killed. The above NOAA chart provides probabilities for both spring
and fall – allowing you to not only plan for spring planting but also for fall
crops. For scheduling fall crop planting
dates, find your first frost date, count backwards the days to maturity (from
the seed packet or tag), and add a few weeks for a harvest window and for the
slowing growth as temperatures drop.
The Problem with Probability
These probabilities are based on past weather data, so keep
in mind that these dates are used as a prediction not as a guarantee. It is especially important to remember this
as weather uncertainty increases with climate change. Last frost could occur well before or even
well after these predictive dates. This
also begs the question – which probability should you use? Looking around at different sources, you
might find sources that use either the 50% or 10% probability statistic, and
there seems to be a bit of disagreement as to which one should be used. Based on the data for my region, I’ve seen
sources share both dates. It really
comes down to how much of a gamble you want to take or how much you want to
push up harvest or maturity. If you plant
on the earlier 50% probability date you may end up having to cover the plants a
few times to protect them from frost.
But each day that passes means that the chance of frost or freeze
decreases.
Whenever I give a talk here at home in Omaha, I often ask my audience to guess what the average last frost date is for planting. Invariably, the answer I get is Mother’s Day…which I guess works as a guidepost in general. However, looking at the data (below), we can see that the 10% probability date for a 32 degree (killing) frost is May 4. The light frost date is May 11 – plants may be damaged but not killed unless they’re very tender. And the 50% probability date for a killing frost is actually April 21, which is the point where the probability of frost is 50% each day (and the probability shrinks each day.
Sometimes produce growers may opt to go early to get vegetables to market – which extends the sales season and allows them to charge a premium price if no other growers are selling. Season extension techniques like high tunnels have also pushed back farm production dates. As climate change makes weather more unpredictable, we may all be finding ways to alter the growing season as a norm rather than an exception. Until then, we’ll rely on the data we have to make the best predictions.
Many gardeners, myself included, have that stash of old seed packets or saved seeds from garden seasons past, just waiting for the right time to be planted. They may be shoved in a drawer, a box, or in the fridge/freezer. Maybe you’re pulling some out of storage to start this spring – will they even germinate? Are those seeds good indefinitely? Do they ever expire? The answer to that really depends on what plant it is and how they are stored. While there isn’t a date where all the seeds go bad, they will eventually go bad over time. Why is this? And how can I make sure to use my seeds before they’re gone? Let’s find out!
Why Good Seeds Go Bad While we think of seeds as perhaps inert, dormant, or in stasis they’re still very much alive and therefore are still undergoing processes like respiration, though at a much lower rate than a growing plant. During respiration, the seed (and plant within) are converting the stored sugars and starches in the endosperm to release energy. Once the germination process starts with the imbibition of water, the respiration rate increases drastically. A large amount of stored energy is needed to get through germination and sustain the seedling until it has its first set of true leaves and can photosynthesize on its own.
Seeds need to retain enough stored energy to sustain seedlings until they develop their first leaves and start photosynthesizing.
The shelf life of seeds is determined by the amount of energy that is stored, the amount used during storage, and the amount needed from germination to leaf development. This means that there’s a limit to how long a seed can stay in storage. After a while the seed loses viability if it doesn’t have enough energy stores to get it far enough along to photosynthesize on its own or to have that first burst of respiration at the initiation of germination. When searching for resources, keep in mind that viability refers to the ability of the seed to produce a robust seedling while germination refers to breaking of dormancy. The terms are inter-related, but the rates are not necessarily the same.
Some seeds have evolved to sit dormant for a long time, while others have a very short lifespan. It usually turns out that the seeds that last longest in storage are weeds that have evolved to wait long periods of time for an opportunity to germinate. Garden seeds tend to be on the shorter end of the storage time scale. A now 140-year old ongoing experiment at Michigan State University has given some interesting insight. In 1880, William Beal (one of the fathers of horticulture) buried 20 vials full of a variety of seeds (garden and weed) in secret locations around campus. The plan was to dig one up every 5 years and see what germinated. However, after the fist few rounds the cycle was bumped to 20 years. A vial was opened in 2000 and only one species, a weed, still germinated. This year is another germination year – we’ll have to wait and see if the mullein will germinate again this year.
How long will my seeds last?
Data from Nebraska Extension publication.
There are a few good sources that pull data from a variety of sources. The figure below lists some life expectancy times for common vegetable crops published by Nebraska Extension, using two common manuals on seeds as sources. You’ll also find some likes to other data, including average storage times for flowers, herbs, etc. in the references section (while we don’t typically promote commercial sites, the guide from Johnny’s Select Seeds has a good list of plants and has a variety of extension and academic sources listed). Like the MSU experiment, most of this research was done a while ago, but the data is still a good generalization. Most sources say that these time estimates are based on storage in optimal conditions. According to Johnny’s Select Seeds, “The actual storage life will depend upon the viability and moisture content of the seed when initially placed in storage, the specific variety, and the conditions of the storage environment”.
What are these “optimal” conditions? Generally the conditions are low humidity and low temperature. Low humidity ensures that the seed stays dry, avoiding potential initiation of germination. Low temperature reduces the respiration rate, slowing down usage of stored energy and increasing longevity. Optimal temperature for storage is below 42°F (15°C). Relative humidity should be between 20 and 40%.
The relationship between temperature and humidity seems to be inverse – meaning that as storage temperature goes lower, humidity can be higher and vice versa. However, storage times increase as both go down. Many sources state that seed longevity doubles for every one percent drop in humidity or five degree (F) drop in temperature. The relative humidity of the air affects the moisture level in the seeds. Germination usually starts at 25% moisture (and above). Ideal moisture levels for storage range between 8 and 12 percent and levels between 12 and 25 can lead to degradation of seeds, growth of fungi, etc. On the flip side, moisture levels below 5% can decrease vigor. Organizations like seed banks and germplasm centers that store seeds long term often will desiccate seeds to around 8% humidity to extend storage, but this isn’t usually needed for home gardeners.
You don’t have to replicate conditions at the Global Seed Vault to have seed saving and starting success
Storage tips Knowing that we need low temperatures and low relative humidity to extend seed life gives us some clues on how to store seeds to get the longest shelf life. This is key info if we’re trying to start seeds in spring that have been stored, or if we need to store extra or saved seeds. For the needed temperature levels, your standard home refrigerator is acceptable. Storage temps for cold foods are around the 40°F mark. However, humidity in a refrigerator is very variable. Humidity can skyrocket when doors are open, as condensation settles from warm room air settling on surfaces accumulates. Auto defrost cycles can also alter humidity. You’ll want to think about a desiccant like those silica packs to ensure that your seeds don’t get too moist. Store them in a plastic bag with the desiccant, and for added protection I always put mine in a sturdy container like a plastic box (or even a canning jar). Storing seeds in a freezer may help with the humidity issue, as any moisture that enters is frozen. You might also want to think about letting your bag or container warm up to room temperature before opening so that you don’t get condensation on the packets or the seeds themselves.
It seems like we’re always adhering to one schedule or another these days. We have devices and planners to keep track of our appointments, our work schedules, kids schedules, and more. Heck, even the antique seed company clock in my office is telling me to order seeds. It can seem overwhelming, so you might laugh if I tell you that coming up with a schedule, or a plan, for your garden can be beneficial. It is especially helpful for vegetable gardeners or those who like to any kinds of seeds.
Developing a yearly plan for the garden can help you keep
ahead of the big tasks, help you stay on top of issues like weather, as well as
make sure you get seeds started on time and transplanting done when it makes
the most sense. While some of this may
be a review for seasoned gardeners, the number of questions and calls we
receive at Extension (and the number of oopsies we see) means that the
information could be helpful for many.
Since my background is in vegetable production, I’ll focus
there with some bits and pieces added for ornamentals when they fit.
Do you have garden
goals?
Whenever you are planning your annual vegetable garden, or planning on
adding any ornamentals to your gardens or landscape, you should ask yourself a
few simple questions. When you’re
dreaming of your garden during the winter is a good time to think of these
goals.
1. What are my goals for the garden?
Do I have long-term goals? What
short-term goals can you set for this year to build momentum toward your
long-term goals?
2. What resources am I willing to invest in the plants I’m ordering
(money, time, water, space)?
3. What are the things I most want to grow?
4. What has worked (and what hasn’t) in your garden in the past?
While it may sound funny to say that you are going to set goals for
your garden, it really isn’t all that far-fetched.
If you are planning to add ornamental plants to your landscape, you
should think about what you want from those plants — are you looking for color
or for structure? how about perennials vs. annuals (or biennials)?
When you are planning a vegetable garden, you should ask yourself not
only what you want to grow, but how much. Are you just planting for
fresh-from-the-garden eating, or do you want to preserve some through canning,
freezing or drying? Are you growing just enough potatoes to eat for a month or
two after the garden season, or do you need to select a variety that keeps well
so you can store it?
Tips for Planning a Successful
Garden
After you set your goals and decide what you want to plant, developing
a schedule of when to do what is a good idea to stay on top of everything. I can’t tell you how many years I had been
planning on planting this or that, but then forget to buy what I need or start
seeds on time. A plan can help with
that, as well as helping you space activities out over time rather than trying
to get everything done in a hectic sprint. This is especially helpful to new gardeners or
busy folks who may forget to start or plant certain things at the right time (I
wouldn’t be speaking from experience here.
Nope, this gardener has never been guilty of that. I meant not to plant all of that garlic that
I bought last fall.) To borrow the method used in a popular self-help book,
you’re “scheduling the big rocks” as one of the habits of highly effective
gardeners.
Keep in mind that it can be hard to “garden on a schedule” as weather
always plays a factor in what we can and can’t do in the garden. Given the wide variability in weather over
the last few years in many parts of the country, which many scientists
attribute to changing weather patterns due to climate change, it can be even
more difficult to pin garden tasks to specific dates. A plan can help you keep track of everything
you need to do, but it should be flexible to take weather into account.
Starting Seeds Indoors
Germinating a variety of plants for our 2018 All-America Selections trials
If you’re starting seeds indoors, decide when you’re going to
transplant them to the garden. You can
usually find this information on a seed packet, but you can find resources or
consult your local cooperative extension office for guidance. Keep in mind that warm-season plants
typically need to be planted after your average last frost date (unless you’re
adventurous and don’t mind gambling with a potential loss). Cool season crops such as Cole crops
(broccoli, cauliflower, cabbage, kale, etc.), leafy greens, and bok choi can be
planted before the last frost date, but usually after the risk of a hard freeze
has diminished. For a map of the average
date for last spring freeze/frost, check out https://www.ncdc.noaa.gov/news/when-expect-your-last-spring-freeze. Note that these ranges are determined by
analyzing the last frost dates over a 30 year period and the actual dates can
vary due to weather variations (made even less predictable by climate change).
Choose the timeframe you wish to plant in the garden and count backward
to when you need to start plants indoors. Put both the planting dates and the
seed starting times on your calendar. Also
keep in mind that this is the earliest that you can plant warm season crops,
but you can plant them later if it works better for you. While we don’t typically share commercial
links on this site, the best resource I’ve found for planning your seed
starting and transplant dates for both vegetable and common annuals is https://www.johnnyseeds.com/growers-library/seed-planting-schedule-calculator.html
Direct Sowing into the Garden
For some crops like root crops, beans, leafy greens, and even some
squash and cucumbers, direct sowing sees into the garden is ideal. You can add timeframes to your plan based on
previous practice, like knowing that you’ll sow carrots toward the end of March
or early April, but keeping an eye on the weather can be even more helpful
here. Success here is more about
temperature than timing. Most plants
have optimal germination temperatures, so you want to sow outside when the soil
temperature (not air temperature) is at or near those levels. The following resource has germination
temperatures for common crops: http://sacmg.ucanr.edu/files/164220.pdf
If you’re lucky, you can search for local web-connected weather
stations that have soil temperature probes.
For example, we have one at our office that we share with clients to
make gardening decisions (http://mgextensionwx.com/). If you can’t find one, NOAA has a few in each
state for official climate data. https://www.ncdc.noaa.gov/crn/current-observations. Putting “check soil temperature” should be on
your garden to-do list regularly until the temps get into good gardening range.
Spreading the planting and harvest through the season
If you’re aiming for harvests throughout the growing season, practice
relay planting where crops mature in shifts throughout the garden season rather
than all at once. If you’re planning on preserving some of your harvest for
winter, planning on larger harvests at certain times in the season can get you
the amount of produce you need for a big batch at the time that you need it.
Some plants are good at producing through the season, but others, like
determinate tomatoes and many beans have a one-time flush of production. Of course, we also have the crops that are once
and done, like carrots and radishes, that only have one harvest. If we space out planting over weeks rather
than planting all at once, harvests (or flowers if you’re growing annuals) can
be spread out over a longer period of the season rather than everything
maturing at once. There’s generally a
several week (to several month) window for planting crops.
For example, tomatoes can be planted as early as the average last frost
date, but can be planted for several weeks afterward. To figure out how late you can plant a crop, look
for the first frost date and count backwards using the “days to maturity”
information for the crop. You’ll want to
add on a few weeks to a month to account for having a harvest window and
slowing growth as temperatures drop.
Keep in mind that many of the cool season crops can last well into the
fall and winter, withstanding frosts and even light freezes, so replanting them
for a fall harvest is ideal.
Planning out when to plant annuals, perennials, trees, and shrubs can
also help make sure you get those plantings off on the right foot and can allow
you to prepare in advance. For example,
if I want to add a tree to the landscape, taking the time to research trees and
planting techniques, scheduling any prep of the planting area, sourcing the
tree, and planting at the right time could all go on your calendar – that way you
are prepared and ready to plant at the correct time.
Other garden tasks
While much of the work of a garden plan is front-loaded to the spring,
there’s lots of tasks that we should be planning on doing regularly. Scouting for and controlling insects and
diseases, removing spent plants, mulching, compost turning, and more all come
to mind. Putting these on your schedule
rather than doing them when you think of
them can really improve your likelihood of getting them done. Also think about some of those big things you
might have identified in the goals you set for the year. Do you want to build a compost bin or develop
new garden beds? Plant some trees? Take a soil test? Putting these on your calendar can not only
help you remember them, but plan ahead as well.
What do you need to do before you build that compost bin? Do you need to buy supplies and tools (and
look for bargains if you’re planning ahead)?
By planning when you’re going to accomplish these tasks, you can plan
for success throughout the gardening year, improve your successes, and feel a
little less hectic when the planting and growing goes full swing.
Regular blog readers will remember that we moved to my childhood home a few years ago. With an acre or so of landscape I finally have enough room to put in a vegetable garden. My husband built a wonderful raised bed system, complete with critter fencing, and we’ve been enjoying the fresh greens and the first few tomatoes of the season.
Jim puts on the finishing touches to our first raised bed garden.
We filled these raised beds with native soil. During a porch addition I asked the contractor to stockpile the topsoil near the raised beds. The house was built almost 100 years ago and at that time there were no “designed topsoils” (thank goodness) – soil was simply moved around during construction. Some of this soil had been covered by pavers and the rest had been covered with turf. [You can read more about designed topsoils in this publication under “choosing soil for raised beds.”] There had been no addition of nutrients for at least 7 years so I was confident that this was about as natural a soil as I could expect.
Our native soil, ready for adding to our raised beds.
I’ve always advised gardeners to have a soil test done whenever they embark on a new garden or landscape project, so before I added anything to my raised beds I took samples and sent them to the soil testing lab at University of Massachusetts at Amherst (my go-to lab as there are no longer any university labs in Washington State for the public to use).
What I already knew about our soil was that it’s a glacial till (in other words it’s full of rocks left behind by a receding glacier). The area is full of native Garry oak (Quercus garryana), some of which are centuries old. The soil is excessively drained, meaning it’s probably a sandy loam. And that’s about all I knew until my results came back.
Some of our massive, centuries old Garry oaks.
Because nothing has been added to this soil for several years, and because I had removed all of the turf grass before filling the beds, I assumed that the organic matter (OM) would be quite low. Most soils that support tree growth have around 3-7% OM. Hah! Ours was over 12%! All I can figure is that centuries of leaf litter has created a rich organic soil.
I never expected this level of OM.
So here’s lesson number one: Don’t add OM just because you think you need it. Too much OM creates overly rich conditions that can reduce the natural protective chemicals in vegetation. This means pests and diseases are more likely to be problems.
I think these may be the lowest P levels I’ve seen in home garden soils.
I was pleased to see our P level was low. First soil test I’ve ever seen in my area where P was below the desirable range! Does that mean I’m adding P? No – because there is no evidence of a P deficiency anywhere in the landscape. And my garden plants are growing just fine without it.
No sign of any nutrient deficiencies here (though the mesclun mix got out of control).
Or here either.
Lesson number two: Just because a nutrient is reportedly deficient, look for evidence of that deficiency before you add it. It’s a lot easier to add something than it is to remove it.
Likewise, our other nutrient values are just fine, and I was pleased to see that lead levels were low. Given that this is an older house that had lead paint at one time, and given the fact that the soil being tested was adjacent to the house, I was prepared for lead problems.
Surprisingly low lead given the original location of this soil next to an older house.
However – we do have high aluminum in the soil. Exactly why…I don’t know. Perhaps the soil is naturally high in aluminum? There’s no evidence that aluminum sulfate or another amendment was ever used. In any case, that was an unexpected result that does give us some concern for root crops. I’ll be doing some research to see what vegetables accumulate aluminum.
The aluminum levels may bear some watching if I’m growing root crops.
Finally, note our pH – 4.9! This is completely normal for our area, which is naturally acidic. In addition, the tannic acid accumulation from centuries of oak leaves has undoubtedly pushed the pH even lower. Are we going to adjust it? Again, no. There is no evidence of any plant problems, and even our lawn is green. Why would we adjust the pH if there is no visual evidence to support that?
No, this is not a typo.
Which leads to lesson number three: Don’t adjust your soil pH just because you think you should. If your plants are growing well, the pH is fine. Plants and their associated root microbes are pretty well adapted to obtaining the necessary nutrients. If you have problems, don’t assume it’s a pH issue. Correlation does not equal causation! You’ll need to eliminate all other possibilities before attempting to change your soil chemistry. And remember it is impossible to permanently change soil pH over the short term. Permanent pH changes require decades, if not centuries of annual inputs (like our oak leaves).
The cat agrees – no pH issue with this lawn.
Will I test my soil again? Probably not. I have the baseline report and since I don’t plan to add anything I don’t expect it to change much. If I had a nutrient toxicity I would retest until the level of that nutrient had decreased to normal levels. But with everything growing well, from lawn to vegetables to shrubs and trees, there really is nothing to be concerned about.
Viburnum plicatum (I think) is one of many established shrubs on the property.
Lesson number four: Unless you have something in your soil to worry about, don’t.
