Roots are the unsung heroes of plants! But unfortunately your every day hard working root gets little respect from gardeners. “We are so taken for granted” whined Radix– “Its just so hard, we are all down here in the dark, nobody see’s us, we get no admiration, yet we work so hard!”. Radix is your every day “working root” mostly ignored by gardeners. Even though the seasons change, and leaves come and go, Radix is growing most all the time! Gardeners love the color of flowers, the texture and shape of foliage, the architecture of tree tree branches and admire all the things plants do above ground. They beautify the world, provide us food, and provide oxygen for us to breathe. We heap our admiration on above ground functions of plants, but without Radix, and all the other roots, the above ground parts would perish.
Growing plants is about growing the whole organism. We may pick the fruit, admire the flowers, or rest under the shade, but none of it would be possible without proper care of root systems. Roots have varied functions—they provide anchorage so the plant can stand upright; they absorb minerals and water; and they store energy in form of starch. Plant shoots grow in the realm of light and much of their adaptations revolve around catching sunlight. Their atmosphere is mostly nitrogen and oxygen. Roots grow in the realm of soil and darkness, their atmosphere is oxygen restricted and dominated by carbon dioxide and even toxic gases like sulfur dioxide, and methane if soil conditions become saturated. Just like all parts of plants, oxygen is required by roots to respire or utilize chemical energy for their growth. Poor Radix can choke if the oxygen supply is limited.
Shoots live in a herbivorous world. Plants get eaten by animals. Because they have buds of all kinds they can grow back, leaves may contain alkaloids and other molecules that reduce herbivory, and plants can arm themselves with spines, thorns and prickles, but roots live in a microbial world. While microbes can grow on most plant surfaces, the root system is bathed in microbes (the soil food web). Not only do roots have to defend themselves underground but they have specific alliances that let them do that! As you know from some of my other blogs, root pathogens can kill all ages of plants from seedling to mature oak trees. The happens when pathogens (which are opportunists) are not well regulated by soil microbes, or when plant root systems are stressed in some way. Large populations of soil bacteria, fungi, nematodes and arthropods limit the development of opportunistic pathogens. These organisms are supported by soil carbon or organic matter which is essential to their abundant reproduction in soil. This carbon is best supplied to root by mulching with freshly chopped Arborist chips.
Roots store carbohydrates made in leaves as starch. This stored energy can be used for their growth or redistributed through the plant later. In order for stored starch to be used, it must be converted back to glucose (by enzymes) and then broken down through chemical respiration. These processes take oxygen which is limited in soil as a function of depth. The deeper you go the less oxygen. This is why trees and most plants have roots in the upper foot or so of soil. This upper foot of soil is sensitive and fragile. It can be compacted by foot traffic or equipment and lose oxygen content. Weed barriers, fabrics, and sheet mulching deprive soil of gas exchange, and the amount of carbon dioxide increases at the expense of oxygen under these barriers. Too much water can fill soil pore spaces causing saturation that usually contain oxygen and decrease the amount of available oxygen since it does not dissolve well in water. All of this also applies to the soil microbial communities which also require oxygen to grow and thrive.
So how do we respect Radix and all the other hard working roots? Promote soil health by avoiding tillage and cultivation. Use Mulches made from fresh tree trimming chips, avoid compacting soils with machinery, and do not shock soils with excessive application of manure, fertilizer, or water which can perturb the microbiology of a soil. I also suggest you learn to admire roots for all that they do for plants in your garden. Check in with Radix every now and then by digging down and looking at root systems. See if they are growing. Try to learn the seasonality of peak root growth so that you avoid practices that may harm roots during their critical growth periods. Be alert to the symptoms of root rot on garden plants especially at the tops of plants such as leaf drop, shoot dieback and wilting.
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
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.
Gardeners often struggle to grow plants in containers. You may feel that you have a really black thumb at times when newly planted seedlings fall over dead or fail to thrive. The problem may not be disease or poor gardening acumen but rather your container media otherwise sold as “Potting Soil”. A trip to one of the big box stores or a larger retail nursery will offer gardeners many choices of bagged potting soils. They are marketed to give you the impression they will grow anything and everything. But do they? Over the last couple of decades I have done comparative potting media trials where I plant small plugs (usually impatiens) three per six inch container. I go out and find every retail brand of potting mix I can find and plant them all up and then follow them for about two months. I’ve been thinking of revisiting the studies and seeing if anything has changed. I also want to test the assumption that you can’t predict the grow ability of a potting soil by reading the ingredient label as some research suggests. While there can always be a surprise with any given product, I think that from my many trials I can make some suggestions to improve the outcome of your gardening adventures in containers.
Growing media is not the same as soil. Since media are placed in containers, often plastic ones, they need to be very porous. Porosity of up to 50% is not uncommon in container media. The bulk of the media needs to hold water and minerals for plant growth. Usually an organic material that has a high cation exchange capacity is used. The darling of potting mixes has been Peat Moss. Since peat moss harvesting is damaging to the environment (see previous blog by Linda CS), many gardeners may want to avoid media with peat moss. Bulking agents that do not hold much water or nutrients are also added to “lighten” or aerate the medium. Horticultural perlite (expanded volcanic glass) is the most common. Sand is also sometimes used but it adds weight to the bag and is not preferred by manufacturers. Some media use bark or other wood products to provide greater porosity. There are usually about 18 to 20 different media on the market at any given time and the results of growing plants in them is predictable. About 10 of the media will not grow anything very well, 5 give ok results and about 5 of the products will grow a nice plant. A lot of the reason for success or lack thereof is about nitrogen chemistry. If no fertilizer is added, the medium will likely not grow well. You can add your own fertilizer and make about ½ of these poor growing media work. One quarter to one half a teaspoon (approximately 2gm) of ammonium sulfate usually peps up most media that are ok but lack nutrients. This is an amount used in a standard height 6inch (15cm) diameter plastic container. Larger containers and plants will require incrementally more fertilizer to achieve growth goals. Some media will not grow even when fertilized. This is because they may contain manures, or composts and manures that have added too much salt to the medium. Adding fertilizers to these products only makes them less growable. Sometimes these potting soils will improve with leaching but then fertilizer will need to be added back later to make up for what was leached away. Generally a salty potting mix is worth avoiding. So how can you tell if you are getting a good or bad mix. You can start by reading the ingredient list. And you will need to decode that list to help you make some decisions. What manufacturers call things can be very misleading. Look for a medium that has fertilizer added and lists what kind of fertilizer was used. These media usually grow without help. Avoid media that use manures, they are not suitable container media ingredients.
Some potting soils claim they can grow plants bigger than others, some claim to be all organic and some claim to be friendly to the earth. This is all marketing. Look for a simple ingredient list that is fortified with a nutrient charge (fertilizer). Begin there. You may want to sieve the medium to remove large particles if you are growing seeds, add more bulking agent (bark, sand, perlite, pumice) for plants that need increased porosity such as orchids, bromeliads and cactus. Don’t be afraid to modify potting mixes to suit the needs you might have. If plants don’t grow, consider adding more nutrients. After growing for some time (months to years), many media will breakdown, and the plant will need to be repotted in a new medium.
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.
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?
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.
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.
If you’ve been reading this blog for a while, you might remember that I got rid of our lawn (getting rid of your lawn post) at our Seattle house . It took too much water to keep it green in the summer, and the resulting ornamental landscape was more ecologically diverse and aesthetically pleasing for such a small site.
But that was then, and this is now. In 2017 we moved back to
the family farm, which has a full acre of landscape – including lawn. Although
we are slowly reducing the vast expanse of lawn, we will keep part of it
because (1) we are on well water and there is an irrigation system and (2)
because we are allowing the lawn to become a diverse tapestry of different
plant species – an ecolawn, if you will.
When I was growing up, my father fought unsuccessfully to keep the moss and weeds out. I happen to LOVE the moss and the fact that it grows here has nothing to do with poor drainage or anything else. It grows here because the environmental conditions support its growth. I love the spongy feel of the underlying moss, and it reduces the amount of mowing necessary because it’s limited in height. And no fertilizers or pesticides are needed.
Speaking of mowing…I hate gas powered mowers. They’re smelly and noisy, they contribute to air pollution, and when something goes wrong you have to take it to small engine repair. These excursions are infrequently successful but always expensive. So imagine my delight is discovering newer battery-powered mowers! All you have to do is swap battery packs. They are quieter, there are no emissions, they don’t smell, and they have an electric engine! No small engine repairs, and they are also lighter for this reason.
I was even more excited to find compatible leaf blowers. We
have tons of Oregon white oak leaves, and we blow them into the beds. We do NOT
leave them on the lawn, because they interfere with some of our non-grass lawn
inhabitants. They are perfect on the beds because their curly, rigid structure
prevents compaction and they keep weeds out while allowing water and oxygen to
Finally, our ecolawn allows me to see and appreciate the
reproductive structures of our mycorrhizal fungi. I don’t even pretend to know
the species and whether they are edible. I just love the fact that they appear
every fall after we’ve stopped mowing.
Sometimes lawns aren’t appropriate, as we found in Seattle.
But sometimes they are – and as long as they are cared for in an
environmentally sustainable manner, they shouldn’t have to be something we
Last week I helped to train Master Gardeners about pruning fruit trees. January and February are the months that we recommend fruit tree pruning in Southern California. In colder climates, pruning may not occur until later when freezing temperatures are minimized and there is less chance of damage to new growth. While trees don’t “need” pruning to bear fruit, pruning practices can enhance fruit production, promote earlier fruiting bearing buds, and increase fruit quality if done in an informed way. In many respects, modern fruit trees have been bred for big fruit, and pruning might need to be done to prevent limb breakage, reduce the number of fruit and position it in the tree fore ease of harvest. Misinformed pruning can lead to disease or loss of bearing wood. “Fruit tree” is a broad category, but for this blog, I am referring to deciduous trees (not subtropicals such as citrus, avocado, mango etc.). Two main categories are common: Pome fruits such as apples and pears and Stone fruits such as cherries, plums, apricots, peaches, almonds and pluots.
The first thing to figure out when pruning any tree grown for fruit production is where the fruit will be formed. This requires examining and understanding buds, twigs and the age of growth that is produced. Second we need to understand the tree’s responses to pruning and how that will affect future fruit production. Finally an understanding of negative consequences of pruning is essential.
Why prune you ask if trees will produce without pruning? Pruning shapes a tree, and helps to create fruiting buds that are conveniently placed for harvest-this keeps fruit pickable with less time on ladders. Pruning gives an opportunity to remove fruiting buds thereby invigorating remaining buds and increasing size and quality of the fruit that will form with less fruit thinning later. Pruning also gives an opportunity to remove diseased, damaged, tangled or infested branches. While various training styles can be used for structural pruning of young fruit trees the open vase or modefied central leader systems are preferred and descriptions of them can be found in extension leaflets. For my own trees I usually do not prune them the first year after planting in order to encourage a stronger root system. In the second and third years I pick scaffold branches or train branches on the central leader.
Fruit is produced on various aged twigs or branches depending on tree species. Peaches produce fruit on growth from the previous year or one year old wood. Since peaches grow vigorously fruiting wood ends up on the outside of a tree. Heading back (or heading) cuts (reducing last year’s branches by at least half their length) will remove ½ the fruit and stimulate buds lower in the tree that will make more fruiting wood. For this reason peaches are usually pruned “hard” to stimulate maximum amounts of fresh fruiting wood. Apples, Pears, Plums, Cherries and Apricots produce most of their fruit on small side branches called spurs. Apples and Pears may also produce fruit from the terminal bud.
Young trees often make many long whips and these are usually headed back (heading cuts remove the terminal bud) to stimulate spurs in the following years. Once the overall shape and size of the trees are set, less pruning is required as spurs may produce fruit over decades of time. As trees mature spurs build up so removing densely clustered spurs on mature trees with thinning cuts (removing an entire branch, spur or twig) will increase the size and quality of fruit formed on the remaining spurs.
Pruning is often used on newly planted trees to form the structure of the tree. When forming the branch structure do no indiscriminately head back every branch as this will stop the growth of the branch that is headed. New growth will only resume from buds that are released to grow. Think carefully about what you want to grow and what you want to slow-down in growth. Pruning is always a growth retarding practice. Branches are best spaced up and down and around a central leader. In other training systems for stone fruits one heading cut when the tree is just a whip will create an open vase shape where all the branches arise from a single point on the trunk. While this is considered a branch defect in shade trees, it is a convenient training system for fruit trees if you don’t let the tree get too large and manage the fruit loads that are produced. Trees trained to a modified open center where branches are spaced on a central leader have stronger branch attachments and can bear greater fruit.
As trees age and grow they require regular training with heading cuts to shorten vigorous branches of peaches or thinning cuts to remove whips, water sprouts or other unwanted branches. Be careful not to over-prune especially in summer or sunburn can result. When fruit sets in the spring or early summer it can be thinned by hand. This form of pruning will increase size of the remaining fruit and quality. Summer pruning is sometimes practiced on very vigorous trees to slow their growth and invigorate buds for the following spring. Prune with care in the summer espeically on green barked trees like apple and pears to avoid sunburn.
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
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
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
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
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
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
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.
[This blog post has been provided by Bec Wolfe-Thomas, an administrator for the Garden Professors blog group on Facebook.]
Woodpeckers (Picidae) frequently get a bad rap from gardeners. It’s often their impression that the birds irreparably damage trees, but this is untrue. Most woodpeckers are insect eaters; they can hear insects under the bark and in the wood of trees. They then target their drilling with uncanny precision to get their meal. This removal of insect pests, such as emerald ash borer, benefits the tree.
And what about the feeding holes left in the tree? This is an exciting bit of tree physiology! Trees are able to compartmentalize or isolate the wounds. After the woodpecker has made a hole to retrieve the insects within, the tree starts compartmentalizing the wound. How long it takes for a tree to compartmentalize a wound and close it depends on species and climate factors.
Below are photos of woodpecker holes in various states of compartmentalization, from freshly drilled to completely compartmentalized and closed holes. Woodpeckers help keep trees healthy by preventing large pest infestations. And while the small feeding holes might be an aesthetic concern to gardeners, they’re only temporary. They will eventually be compartmentalized and closed, and the tree will be healthier in the long run by having fewer pests.
[Please note the larger holes excavated for nesting will compartmentalize but will not close over time.]
California had the worst fires in the last two years of its existence as a state. Hundreds of thousands of acres of brush and forest burned. More importantly thousands lost their homes as fires moved across urban/rural interfaces to destroy communities. The entire town of Paradise, California was burned to the ground. Here in Ventura County, the Thomas Fire was the state’s largest fire by the time it was done, and hundreds lost homes. No other time in history have we been so focused on what will burn, why it will burn, and what we can do to have a “firewise” landscape.
Fire authorities around the world have advocated creating defensible spaces around homes that are clear of ignitable vegetation. Some authorities have mandated by law that mulch, pine needles and other debris be removed as a fire prevention measure near structures. There is a general recognition that any plant can burn. Even well irrigated plants will rapidly desiccate and become flammable in the face of strong wind and a heavy fuel load that is inflamed nearby.
Flammability of landscape around homes is dependent on several factors. Vegetation placement can obstruct or allow for fire fighters ability to reduce damage to a home. While it is natural to assume that avoiding flammable plants is a part of this process, there is no standard method for testing plant flammability. Many lists of firewise plants have unknown origin or are just guesses. Flammability can be assigned four dimensions: ignitability, sustainability, combustibility and consumability. These factors refer to time till ignition; time a material will burn; rapidity or intensity of burn and quantity of material that will burn. The components of combustion are influenced by moisture content, percentage of carbon, percentage of volatile compounds; surface area to volume ratio and other factors. The varied factors are usually not all studied at the same time and are not all equally important to plant flammability. Thus assessing flammability even within the context of a controlled study will only partially assess a material’s likelihood of burning under various conditions. Hence most of the lists are not that helpful.
Behm et. al. showed that variations in flammability between plant species exists, and also that species within the same genus can vary widely in their flammable nature. Thus lists should not assume species in the same genus all have the same flammability. There is some thinking that flammability is an evolutionary trait that some plants exploit to their benefit, i.e. they are made to burn, such as the California Chaparral plant communities. Simply burning fuels in a laboratory setting does not take into account many of the factors associated with fuel burning intensities. Species differences notwithstanding, the amount of dead plant matter (dead twigs and leaves) vs. live matter, the arrangement of leaves, mulch and adjacent species all play a role in the flammability of the landscape itself which cannot be studied in a lab setting. Landscapes are “fuel bed complexes” with multiple elements that are not replicated in studies. For instance, small leaves from some shrubs ignite easily, but when burned as litter, develop low heat release rates because of poor ventilation.
Testing live plant materials alone is misleading because the flammability of an intact shrub is caused by the interaction of live matter with “necromatter”. Dead tissues are thermal catalysts which ignite live material. The ratio of necromatter to live matter influences flammability and is generally not well studied. Fire modelling also has a role in understanding what will burn. Both wind and slope increase the spread rate and the fireline intensity of burnable plants. Fire behavior characteristics on a given plant also are affected by both its physical and chemical characteristic — tissue mineral and water content have impacts on flammability. This bodes poorly for firesafe plant lists because lists do not consider plant physical or chemical attributes and if moisture levels are low it will burn regardless of its structure and geometry or its status on a list. Sometimes though a dense wall of well hydrated vegetation can save homes such as the avocado orchards that held back fire in the Thomas Fire in Montecito, Ca.
While lists don’t satisfy scientific rigor they are great for policy makers and homeowners who want to know what to plant. Unfortunately many lists are just compilations of other lists, none of which were based on research. Sometimes lists confuse one desirable characteristic with another, such as native plant lists that tout drought tolerance. Many drought tolerant plants are not fire resistant especially after a long dry period, indeed they often evolved to burn under such conditions.
For those that live in fire prone areas, fire resistant plant lists will always be an attractive or even required element of landscapes. Lists will not save a structure in the face of high winds and adequate fuel or embers. A defined defensible space around buildings, and maintenance of plantings that removes dead matter, maintains irrigation, and maintains proper distance from combustible surfaces will be more effective than choosing landscape plants from flammability lists.
Fernandes, P.M. and M. G. Cruz. 2012. Plant flammability experiments offer limited insight into vegetation—fire dynamic interactions. New Phytologist 194: 606-609
Behm, A.L., M. L. Duryea, A.J. Long, and W.C. Zipperer. 2004. Flammability of native understory species in pine flatwood and hardwood hammock ecosystems and implications for the wildland –urban interface. International J. of Wildland fire 13: 355-365.
White, R.H. and W.C. Zipperer. 2010. Testing and classification of individual plants for fire behavior: plant selection for the wildland-urban interface. International J. of Wildland Fire 19:213-227.
Believe it or not, a
cactus, of all things, is one of those plants that have come to represent the
holidays and feature in the regular rotation of holiday houseplants. Then
again, maybe it isn’t so strange amongst its peers that feature a flashy bulb-grown
plant named for a horse’s head (the Latin name of amaryllis is Hippeastrum,
literally meaning horse flower), a plant that has ugly flowers but brightly colored
leaf bracts and leaks sticky and irritating latex when damaged, or some
daffodil-like flowers that have musky odor so strong it makes some people nauseous. But…..I digress.
Back to the
cactus. However you see it though, the
cacti that make their debut at the holidays are suffering under a case of
mistaken identity. What you typically
buy as a Christmas cactus is not a Christmas cactus at all. It is actually a
Thanksgiving cactus. Now this wouldn’t
be such a big deal, except that there is such a thing as a “Christmas cactus” —
but you won’t find one on store shelves. Nay, it is hard to even find one in
garden catalogs. And this is sad,
because the Christmas cactus is, I think, even more beautiful than the
How did we end up
ignoring the beautiful Christmas cactus in favor of its holiday cousin? It all comes down to timing and how we buy
things for the holidays. It seems that,
as the shopping and holiday seasons creep ever upward on the calendar,
retailers have little love for a cactus that is actually programmed to bloom at
Christmas. They need something that blooms earlier so that it can be on the
store shelves as early as possible. (At this pace, breeders will need to
develop and Independence Day cactus for the Christmas shopping season.)
Thanksgiving cactus has been rebranded as a impostor stand-in for the
true Christmas cactus. We won’t even talk about the Easter cactus, which just
totally feels left out of the family (and yes, there is such a thing and it is
These cacti were in cultivation in Europe by 1818 and various different species were being hybridized, probably most notably by W. Buckley. The most notable hybrid, bred now named Schlumbergera ‘Buckleyi’ is considered to be the first actual “Christmas cactus” and associated S. x buckleyi hybrids are still grown as Christmas cacti. Cultivars and crosses of S. truncata are the Thanksgiving cacti that have been rebranded as Christmas cacti. They can be identified by their flattened stems (or cladodes or cladophylls) that have spiky, toothed edges and zygomorphic (now that’s a fancy word — it means that they have a two-sided, or bilateral, symmetry) flowers. Most of the Thanksgiving cacti that have these characteristics.
You’ll most commonly
find them in pink colors, but you can now find them in yellowish colors. The
flower shape often leads to its nickname: “Zygo cactus.”
S. x buckleyi are the true Christmas cacti and form what is
called the Buckleyi group. Most of these
have characteristics that come from the species S. russelliana, which
was used in the early Buckley crosses. They can be identified by their rounded,
less pointy cladodes and round, radially symmetrical flowers. They do have a
similar growing form, but those in the know can tell the difference.
And for those
following along at home, the Easter (or spring) cactus used to be considered part
of the Schlumbergera genus (S. gaertneri) and then the Rhipsalidopsis
genus, but now is classified as Hatiora gaertneri has radially symmetrical
flowers but the cladodes are three dimensional rather than flat, elongated, and
scalloped. They have a wide range of
colors, such as red, pink, and even orange.
Holiday cactus care
It’s a cactus, so it
should be easy to care for – I just water it sparingly and keep it dry,
Whether you have a Thanksgiving
or Christmas cactus (or an Easter one, for that matter), you take care of them
the same way. Keys to their care come from their native habitat, which is not a
desert but the cloud forests of costal south-east Brazil. The high-altitude costal areas where they’re
from are cool, shaded, and relatively humid with the mists and moisture rich
air. They are epiphytic or lithophytic – meaning that they grow on trees and in
crevices with decaying plant material rather than in the soil. And while you don’t need to know this to grow
them, the morphology of the flowers have developed to support the feeding of hummingbirds
which act as their main pollinator.
Since we don’t grow
them epiphytically, when we pot them we need to make sure that we provide a
light substrate for them to grow and to get plenty of oxygen to the roots. Potting
mixes should have a high ratio of peat or coir and even some bark or other
coarse woody material. As for watering,
you’ll want to keep the soil fairly moist, rather than dry. You’ll also want to let them dry slightly
between watering, but don’t think that they like to live the life of
dehydration — you do need to keep them watered.
One of the reasons that
they bloom at very specific time of year has to do with light and, to a lesser
extent, temperature. They are short-day
(or rather long-night) plants, so they
flower as days grow shorter (or longer, in the case of the Easter cactus) and
nights grow longer. The Thanksgiving
cactus will bloom with just a little shorter dark period than the Christmas
cactus, which is why it blooms in late fall as opposed to the Christmas cactus
that blooms closer to when days are the shortest around the solstice. They will also bloom better and longer if
they have cooler temperatures, so keeping them in a cool area of the house is
ideal. In high light situations the
cladodes will turn red. Keeping them too
dark, however, will limit growth and keep them from thriving.
Since they are
short-day plants, the plants need a period of several weeks where the period of
darkness at night is 12 hours or longer for their flowers to begin
forming. This occurs naturally about
mid-October, but you can delay flowering by using grow lights to lengthen the
day (or keep in mind that bright indoor lights can also limit or reduce
blooming). Also, don’t be alarmed if
they bloom at odd times through the year. Since daylight coming into your windows can be
altered by window treatments or films, the light levels can technically be “just
right” for flowering at multiple times per year. In my old office the tint on the windows
created the right conditions at least once or twice per year – one year I had a
Halloween cactus and the next it was a Memorial Day cactus.
If your cactus does not flower, you need to move it to a spot where it gets at least 12 hours of relative darkness to initiate blooms (keep away from indoor light sources or windows near outdoor lights). Hopefully, you’ll have lots of colorful blooms for Christmas…..or whichever holiday your cactus celebrates.