California “Big Trees” under threat

It’s not my week to post on the blog, but this is a PSA for California residents. Having visited the Capitol grounds in Sacramento, I find it important to make others aware of the plans to remove a number of large and historically important trees for the purpose of building a parking garage and expanding the Capitol building space.

I’m not a California resident, so in a sense it’s none of my business. But I am an urban horticulturist, and an arborist, and committed to preserving trees especially in urban environments. These trees are irreplaceable unless you want to wait a few hundred years. The plans to “relocate” some of these large trees are probably not realistic given the size of the specimens.

More importantly, this is public space and the public should be actively involved in discussions. But the process has been secretive and under the radar of a public more concerned, and rightly so, about COVID-19 and all the associated fallout from the pandemic. But it’s not too late.

Please share this post with California residents who have should have a say in how their land should be managed.

For those Californians interested in supporting the effort to save the trees at Capitol Park and call for the development of a Park and Tree Management Plan, you can sign the petition at https://www.change.org/p/california-state-legislature-save-california-state-capitol-park.

More importantly, you should call AND write to your own California legistator at this website findyourrep.legislature.ca.gov, as well as the two Legislative leaders who can really pause the project and guide its re-planning:
Senator Toni Atkins, President pro-Tempore of the Senate, 916 651 4039 and senator.atkins@senate.ca.gov. UPDATE: This email does not appear to work. Try using this form.
Assembly Member Anthony Rendon, Speaker of the Assembly, 916 319 2063 and speaker.rendon@assembly.ca.gov

Falling forward: Time to plan and plant the fall veggie garden

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. 

Update on our bare-rooted perennial garden

Our south-facing pollinator garden.

Two years ago I installed a pollinator garden in early July. This goes against my recommendation to install plants in the fall, when roots have longer to get established and less stress is felt on the rest of the plant. But I wanted to see what would happen if I was careful to mulch well and keep it irrigated. Oh, and did I mention I was going to root wash every one of them? (Be sure to look at that process in the link from 2018.)

I reported on progress last year, and this year shows even more vigorous growth by nearly all the plants. Two of the three ‘Bandera Purple’ lavender died over the first winter, as they were marginally hardy (USDA 7-10) for our area. One straggler remains in the lower right hand corner of the photo below. The Agastache ‘Acapulco Red’ and the Verbena ‘Homestead Purple’ were planted near the front of the beds on both sides and while they survived the first year, they are now gone. My guess is that our cold snap in February 2019 wiped out those plants that were in less protected locations. Perhaps we’ll fill those spots in later with something more cold hardy, or just let the escaped Viola tricolor continue to colonize bare spots.

Overall, the garden is wildly successful in attracting hummingbirds and a variety of native bees and other insects.

The southwest garden is being colonized by violets that have hopped out of a nearby container. Wood chip mulch keeps the soil cool and moist.
The southeast garden with its invading strawberries (soon to be relocated). The tiny lavender in the back right corner is a rescue plant.

I still have a little work to do – I’m relocating the strawberry adjacent to the southeast garden so it stops invading the perennial bed. But after that I’m calling this garden finished.

Summertime pruning

Summer is a time of bounty in the home garden. During June, July and August the majority of small fruits ripen on home orchard trees. Plant health care is important to consider in advance of summer bounty. Careful dormant season pruning, dormant sprays, mulching and care helped to produce a nice harvest. As the fruit comes off the tree, some summertime options are available. This is a time when some limited summer pruning can be done to manage the physiology and growth of many fruit trees. Even some citrus will benefit from careful summer pruning.

Summertime brings a harvest bounty for many home gardeners, and with it an opportunity to modify tree growth with pruning

One obvious reason to prune in summer is to repair broken and remove dead branches that may have occurred from excess fruit weight or other injuries. Breakage is common in peach, plum and apples if fruit loads are not thinned earlier in the season. Cut the broken branch from the stem it attaches to with an angled cut that leaves the branch collar intact. Do not cut branches flush with the stem they were attached to. Many years ago the myth of flush cuts for shade trees was found to permanently damage trees, but flush cuts are often still practiced on fruit bearing trees. Flush cuts allow decay organisms to enter trees leading to heart rot and other kinds of wood decay.

Sporophores or fungal fruiting bodies indicate the presence of wood decay in trees. Usually be the time sporophores are showing wood decay is extensive in the tree.

Another myth that persists in home fruit orchards is painting wounds with a ‘sealant’ or ‘protestant’. There is no reason to paint cuts. They do not limit the progress of decay or prevent decay from forming behind the paint. Pruning paints do not promote “healing” or callus formation to close the wound. There is some thinking that pruning paints may even accelerate the process of decay formation. So throw away the black tar, it has no practical purpose in support of pruning.

Pruning paints are a relic of past horticulture traditions. They have no place in modern arboriculture or pomology

While pruning paints are no longer used, paint has other functions that can be helpful. If a large branch was removed from a tree, sometimes the remaining branches may require protection from sunlight. Apples and other thin-barked trees (citrus, cherries, etc.) are very susceptible to sunburn. If branches that were previously shaded are suddenly exposed to high light levels, the bark can be destroyed leading to sunburn cankers and entry of disease-causing fungi such as Botryosphaeria spp. If repair pruning exposes a large gap in the canopy, it is appropriate to apply white wash or diluted white latex paint to exposed branches in order to protect them from bright sunlight. The most severe damage occurs on southern and west facing branches. Sunburn is one of the leading causes of abiotic damage and a predisposing factor for disease such as stem and branch cankers in apples.

Fireblight is another common disease on pears and apples and develops after bloom. Pruning out fireblight affected twigs helps to arrest disease progress. Finally, bacterial canker can be devastating to Prunus (plum, cherry, peach, nectarine and almond) in parts of the country with warm summer rains. Immediate removal of bacterial canker affected branches is necessary to prevent permanent damage to the tree. Tools used to remove cankered branches should be sanitized by flame (torch) or with disinfectants. Canker diseases are active in the warm summer growing season. Cankers can be caused by bacteria or fungi and should be dealt with as soon as symptoms are noticed. The earliest symptom of an active canker is slowed growth relative to other branches on the tree. Slowed growth results in smaller leaves and fruit and fewer leaves. Affected branches seem more open and just look “weaker” than their healthy counterparts. Slowed growth is often followed by wilt, leaf drop and eventually necrosis or death of the branch. It is best to remove diseased branches early before the organism spreads to the main stem. Since symptoms occur when leaves are on, summer pruning is the best approach to remove cankered branches. Regardless of where or when damage occurs, using correct pruning practices should be adhered to.

Cankers kill branches in fruit trees, they can be caused by either bacteria or fungi. Here Botryosphaeria dothidea has killed a branch in this apple.

Healthy growth on the tree above but thin, weak, small leaves on the tree below indicate a developing branch canker.

Pruning is used most widely on fruit trees to dwarf them so that fruit is produced at a height convenient for harvesting. Pruning creates two universal responses that apply to all woody plants:

I. Pruning is growth retarding. The part of a tree pruned will grow less than the unpruned part. Or, a pruned tree will grow less than an unpruned tree.

II. Pruning is a bud invigorating process. A pruned tree or branch will have more of its buds released to grow compared to the unpruned branch or tree where many buds remain in a dormant state.

The more a tree is pruned, the less its roots and stems will grow. Even though the more a tree is pruned the more latent or axillary buds will be released to grow, it will not be able to make up for the lost leaf potential of the unpruned tree. The pruned tree has reduced photosynthetic capacity, makes less energy and will grow less overall. The thing that is not very clear is how the timing of pruning affects the basic processes. In his review, Chandler makes clear that pruning in the dormant season will retard the growth of apples less than if they are pruned in the summer. Summer pruning also significantly reduces the growth of roots compared to dormant season pruning. Removing leaves in mid-summer or after all shoot growth has stopped (summer rest period), removes photosynthetic capacity and reduces stored energy in the tree, thus retarding growth overall. While buds may be invigorated and new summer growth may occur, this rarely makes up for the tissue lost and still results in growth reduction.

Summer pruning does not result in more fruitfulness the following year, and in apples does not increase the number of spurs formed for fruit formation. Summer pruning can open the canopy and allow branches to form lower down that are useful for easy harvest. The effect of summer pruning on next year’s fruit quality is uncertain. Summer pruning can accelerate the ultimate scaffolding or canopy shape for the mature tree.

Pruning citrus after harvest, during the warm season can affect fruit size in the following year. This may be due to fruit thinning as some citrus have green fruit formed by summer that ripen in winter or spring. Summer pruning removes fruit and remaining fruit can grow larger.

Summer pruning of fruit trees before fruit harvest increases light penetration into the tree and can increase color development of the fruit. Pruning must be done cautiously to avoid excess light penetration and sunburn to scaffold branches and resultant canker diseases. Summer reduction pruning is most often accomplished by pruning the ends of branches back to other branches or twigs. Removing about one half the current season’s wood (on a given branch) will achieve objectives usually without causing excessive light penetration into the canopy. Not every branch need be pruned but an even approach, removing branches consistently around the tree, will maintain form. No more than 15-20% of the canopy should be removed by summer pruning. On some vigorous growing trees such as Persian mulberry, pomegranate, or some peaches, heavier pruning doses can be used. Pears, apples, plums and cherries require less pruning and cuts should be made to preserve spurs and other fruit bearing wood. Some varieties of cherries can become ‘over spurred’ and thinning cuts to remove excess spur wood can sometimes be helpful to limit production and increase fruit quality in the next season.

References:

Chandler, W. H. 1923. Results of some experiments in pruning fruit trees. Cornell University Agriculture Experiment Station bulletin 415.

Ingels, C. and P. Geisel. 2014. Fruit and Nut Tree Pruning Guidelines for Arborists. University of California Agriculture and Natural Resources publication 8502. http://anrcatalog.ucanr.edu

Saure, M.C. 1987. Summer pruning effect in apple—a review. Scientia Horticulture 30: 253-282

Water Wise Gardening: Conserving and Irrigating Responsibly

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:

Drip Irrigation for Home Gardens

Building and Operating a Home Garden Irrigation System

DRIP: Watering the Home Garden

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)

Selected references:

Comparisons of shredded newspaper and wheat straw as crop mulches

Soil Temperature, Soil Moisture, Weed Control, and Tomato (Lycopersicon esculentum) Response to Mulching

Newspaper Mulches for Suppressing Weeds for Organic High-tunnel Cucumber Production

Tools, tips, and terrible traditions for raised beds – Part 3

Young vegetables thrive in mulched, weed-free raised bed.

Over the last couple of months I started a series on raised bed gardens, focusing on materials and preparation. In this final installment, I’ll focus on maintenance activities to avoid in your raised bed systems and remind you of three things you should always do.

Terrible traditions

We’ll start with some practices that damage soil structure and function (GP John Porter discussed this in much detail a few years ago). Tilling, once the mainstay of soil preparation for crops, is increasingly found to cause more damage than good. Grinding the soil into a material with the texture of coffee grounds might look pretty, but it’s devoid of the ped structure that allows water and gas to move through easily. It also increases microbial activity by bringing up microbial spores, which release carbon dioxide to the atmosphere as they digest whatever organic material is there. And tilling will increase the likelihood of erosion and compaction.

Soil runoff from tilled, unprotected field. The same thing will happen in your garden. Photo from Wikimedia.

This is the opposite of what gardeners should want: an optimal soil has natural structure which might look messy but allows for good drainage. It’s also more resistant to compaction and erosion, especially when it’s protected with mulch (more on this later).

Speaking of drainage, don’t be tempted to add gravel or some other coarse material at the bottom of the bed. The change in soil texture creates a perched water table, which makes for a soggy planting bed and optimal conditions for soil-borne diseases.

Classic experiment that demonstrates water does not move easily through different soil textures.

While we’re talking about unnecessary or harmful additions to your raised beds, let’s not forget the annual addition of compost or other rich organic material. This is a holdover from old agricultural practices and is not warranted unless you have an organic material deficiency. Without a soil test, you don’t have a clue about what your soil has or what it needs. The problems associated with routine amendments are discussed in this peer-reviewed fact sheet, and are exacerbated by the tillage that is often the means to incorporate compost. Likewise, don’t add fertilizers and pesticides unless you have conclusively identified nutrient deficiencies or pest issues.

If your nutrients are off scale, don’t add any fertilizer!

The last tradition I’d like to see shelved is growing cover crops. This practice originated in the management of agricultural fields, which were otherwise left bare after harvest. Outside of producing some kale or other winter vegetables, what’s the point of planting a cover crop in your garden, when you can protect the soil in other ways? Cover crops require water and nutrients, which eventually will need to be pulled or incorporated. You are forcing your soil system to continue to support plant growth and be subjected to disturbance with the planting and harvesting of the cover crop. Why not let the soil rest over the winter with a nice blanket of mulch? Give it a chance to regenerate its nutrient load while being protected from unnecessary disturbance.

A great arborist chip mulch has leaves or needles as well as wood.

Three tips

Two of these tips have been discussed many times in this forum, so I’ll direct you to longer discussions of soil testing and mulching. Mulching is not just important for protecting the soil bed after the growing season, but should be used on actively producing beds. A deep, coarse organic mulch will promote water and air movement, moderate soil temperatures, reduce weeds, and provide a slow feed of nutrients throughout the season. You’ll have to wait until your seeds are up to apply it, of course, but try to avoid bare soil as much as possible.

Though you’ll need to leave the soil bare during seed germination, you can still protect unplanted areas of the bed with mulch.

Soil testing is really crucial for any garden, but perhaps most important in vegetable gardens where harvesting may decrease key nutrients over time. It will also guide you in identifying potential heavy metal problems. The money you will save in not buying unnecessary fertilizers and other amendments will pay for many soil tests.

There is so much great information in a soil test that will help you make decisions about what to add – and what to avoid.

Sometimes you will need to add material to your existing beds if you are not using a natural soil. Soilless media (deceptively marketed as “potting soil” though no soil is to be found) will decompose and settle over time, leaving you with a sunken soil system. You will need to add more of the same sort of media to the beds, making sure you mix it in thoroughly to prevent a perched water table. (This is why you might consider using a natural soil and avoiding this annual chore – because a natural soil will not subside over time.)

This recommended planting media will decompose down to the oyster shells and lime over time.

The weed apocalypse

I have been hiding from COVID-19 in Arizona, but I had to return to Ojai, Ca because I was “noticed” by the local fire department to abate my weeds. I returned to find the Weed Apocalypse (WA 2020). Late spring rains were spaced nicely in California supporting rampant weed growth. So, why did this happen? What can I do about it now? How could I have better prepared for WA 2021 next year?

The Ojai “Weed apocalypse”. This is what happens when you leave and do nothing in your garden for two months.

In May, the days are getting noticeably longer and moving closer to the longest day of the year (June 20–the summer Solstice). Longer days add more photosynthetically active radiation and put plants on a rapid growing phase at this time of the year. If water and soil nutrients are not limiting, this is the fastest growth period for most plants. Weeds have the unique quality that they will grow faster than many garden plants even with less resources. When resources are plentiful, they grow  faster still.

One way to prevent the weed apocalypse is to deteriorate the weed seed bank . The “weed seed bank” (WSB) is the amount of seeds stored in soil that are viable. The seed bank is restored each year when weeds set seed and drop them on or into the ground. In some cases the seed bank also includes plant parts such as Bermudagrass (Cynodon dactylon) stems and rhizomes (underground stems) that can lie quiet but, once sufficient moisture is available, they spring into life! So once the weeds set seed, just “whacking” or mowing and leaving the mulch behind does not usually solve the problem as viable seed is added to the WSB. Annual weeds can be reduced substantially if they are controlled prior to seed set.

Weeds are sneaky buggers. They imbue their progeny with germination inhibitors or dormancy factors that delay germination. Some seeds complete their maturation even when they have been cut away from the main plant. This is why weeds always seem to be there for you. When dormancy factors wear off, or are washed away seeds will germinate. So after a strong rain event or irrigation weeds emerge that were previously dormant. Some of the seeds remain dormant in the WSB as a back up opportunity to grow. In the case of Slender wild Oat, Avena barbata, it has two maturation ‘stages’ that take advantage of both early spring and late fall rains, with seed ripening at both of those seasonal times. Light is also necessary for many weeds to germinate. When weeds are removed by tilling or digging, new seeds are brought to the surface and may now germinate. Additionally, many weeds have the capacity to regenerate if the entire root is not removed. One tenacious weed, Field bindweed (Convolvulus arvensis), is known to regenerate from each node and root as deep as four feet. Cutting the plants into pieces makes more of them!

Weeds can be annual biennial or perennial . Some weeds such as Poa annua or annual bluegrass complete their life cycle (seed to seed) in only a few to several weeks, others grow for years. Annuals survive drought or cold winters as seeds while perennials as roots, tubers or dormant stolons or stems. Biennial weeds usually grow their vegetative body in the first year and reproductive structures in the second year, they are often rosette forming plants that grow close to the ground in the first season and develop tall stocks in the second. Knowing how to identify weeds helps to understand their biology and ultimately control strategies.

Many gardeners are herbicide averse. However, herbicides will often give the most economic and effective control of weeds. Some weeds like field bindweed are only well controlled with herbicides. Herbicides are broken down into two categories: pre-emergent herbicides and post emergent herbicides. Pre-emergent herbicides inhibit seed germination or kill emerging seedlings before they can develop. Post emergent herbicides kill weeds after they emerge from their seeds. Almost all weeds are better and more easily controlled at juvenile life stages. This is true for mechanical or chemical control. Regardless of how you choose to deal with the WA in your garden starting when weeds are small will give you a tremendous advantage.

Like all pesticides, herbicide labeling must be followed carefully to apply the right amount of product at the right time to the target weed (which also must be listed on the label). There are some amazing herbicidal tools that can save hours of labor. Some drawbacks of herbicides are that they may be expensive, may require multiple applications, require equipment to apply as well as personal protective equipment. Herbicides can be selective or broad spectrum. For instance, Fluazifob-P-butyl (active ingredient of Fusilade II) will control warm season grasses in many ornamental broadleaved plants. This is immensely useful since you can apply Fluazifop-P-butyl “over the top” of a flower garden and free it of bermudagrass (Cynodon dactylon) without harm to your ornamental garden plants or other non-grass landscape plants. Other herbicides containing plant growth regulators such as 2,4-D are broad-spectrum and will kill or harm many kinds of broad-leaved plants in turfgrass without harming the turfgrass. There are also some broad spectrum contact herbicides made of soaps or acids that will kill both broad leaved and grass weeds on contact. While these products do not have systemic action they can be very effective on both cool and warm season young weed seedlings. Herbicides when used carefully and following labeled instructions can save hours of hand weeding labor.

In my own yard I have chosen not to use herbicides because I have so many plants that are sensitive to the kinds of products I would need to use. I am pretty much down for other types of control. This month my city council decided to ban the use of gasoline powered lawn mowers–my chief weapon for the WA! We took a chance and used it anyway because our weed issues are so bad. As mentioned earlier the best time to use mechanical control of weeds is when they are in the cotyledon or two leaf stage of growth. A quick attack with a scuffle hoe will wipe them out. When they grow to adult weed size, larger and larger machinery become required.

Once perennial weeds such as bindweed grow a bit they become impossible to control with hoeing because they will grow back from roots. String line trimmers are used for weeding in many apocalypses but have their limitations. Bits of plastic trimmer line break off and pollute your landscape. Biodegradable plastics are usually used, but the idea of littering your yard with plastic bits is bothersome. Limiting the use of oil consuming machines is a great idea, but using battery powered machines has limits. Buying extra batteries so you can destroy while you charge is helpful.

Hand pulling is a great way to release pend up stress (of the human not the weed), get exercise, and rid the garden of apocalyptic pests. However, for some weeds like yellow nutsedge (Cyperus esculentus) you will only increase the problem as nutlets are released from dormancy when you pull the “mother” plant. By the time you see the emerging nutlets they have formed more nutlets so you can never get ahead of the problem. If you decide hand pulling will work, irrigate the day before you want to weed and they will come out much easier.

Mulching with fresh coarse arborist chips is a great way to prevent annual weeds from getting the light they need to germinate. Mulches also break down to improve soil. We have been mulching for a couple decades on my driveway but have not added any mulch for a few years. The broken down mulch and improved soil are now the most apocalyptic weed garden. If you use mulches for weed control fresh chips need to be applied at least annually in a thick layer to be effective. Also constant application of mulches can make soil! This soil builds up without you realizing that the root collar of perennials or trees may be getting buried. If you mulch consistently around trees be sure to keep the root collar exposed.

Not all weeds germinate in the early winter. There are winter and spring or summer germinating weeds. The differing timing of their emergence can happen unexpectedly. Just when you thought you had weeds in control, another set seems to appear requiring your attention. Look for summer emergent weeds when night temperature lows are above 60F.

Using an old glass shower door to solarize the soil and kill weeds. Note some yellow nutsedge is surviving near the edge of the doors.

Solarization is another way to kill weeds. This is the old greenhouse effect used as a weed weapon. Clear plastic laid on the soil surface and sealed at the edges will if exposed to full sun heat the contents to the point of their death. The solarization effect does not penetrate deeply into soil, so if perennial weeds are solarized, they may survive and regrow from root pieces. If you want to try solarizing your weeds purchase thick UV resistant plastic otherwise you will have bits of plastic everywhere as the sun breaks it down into pieces… Warning, this does not work with Field bindweed! In my own yard I have used old glass shower doors to solarize the soil.

Finally if all else fails and the WA is bearing down, you can just eat them. Many weeds are edible and can make good food. Nettle, Sonchus (sow thistle), purslane, dandelion and many of the Mustard family are edible at various stages of their development. Some folks have even collected mustard seeds and made their own condiments. Of course, you should always exercise caution when consuming wild foods. Some contain toxins or other chemicals that individuals may be sensitive to. The Sow thistle and wild lettuce (Lactuca spp.) contain latex which many are sensitive to. The stinging nettle has hairs on its surface that contain an irritant (oxalic acid) that causes skin burning and welts. Others, such as black elderberry may contain cyanide alkaloids in the green tissues-stems, fruit and other parts. Research the risks of consuming or contacting some plants before attempting to eat or handle them.  There is hope, because even the nutlets of one of the worst weeds (yellow nutsedge) are edible…

Viral Vegetables? Growing (and Buying) Produce in the age of COVID-19 (and reducing fear with facts)

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. 

Factsheet: Is Coronavirus a concern on Fresh Produce?

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. 

Factsheet: COVID-19 and Food Safety – Shopping and Handling Groceries

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. 

  1. Wash your hands. The most common pathway of contamination for produce is from human touch.
  2. You should use clean water that you would use for drinking (like out of the tap) and not use any bleach or soap. 
  3. Providing gentle friction with your hands or a produce brush or by rubbing the produce together is sufficient. 
  4. 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. 
  5. When in doubt, discard produce you may think is contaminated or wash it separately. 
  6. 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. 
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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)

You can practice handwashing anywhere. You can buy portable hand washing stations or build this DIY Model. Plans: https://www.youngfarmers.org/fsma_resources/portable-handwashing-stations/

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:

COVID-19 FAQ for Community Gardens

And since some gardeners may sell at (or at least visit) farmers markets:

COVID-19 FAQ for Farmers Markets

Click here for all the resources developed by NCSU

A tale of two weeders – lessons in managing aggressive, perennial weeds

Choose your weapon in your war against weeds!

Nearly every afternoon for the last two months, curious drivers have noticed two people meandering through a pasture, following a narrow pathway formed by two lengths of string tied to fenceposts. It’s us! Thanks to COVID 19, we are no longer able to go the gym for a workout so like many other gardeners we have put that unexpended energy into our gardens and landscapes. And in this case, cattle pasture.

The herd

The lettuce from hell

My family has raised free-range, grass-fed beef cattle for over 50 years, and with our move to the family farm in 2017 we now oversee much of that business concern.  Managing pasture weeds is just one of the battles associated with providing quality browse for the cattle. Inedible plants like bull thistles (Cirsium vulgare) and tansy ragwort (Senecio jacobaea) are taprooted species, easily removed with a single weeding. But not Canada thistle (Cirsium arvense), colorfully and accurately described as the “lettuce from hell” thistle. Though it’s highly nutritious, the prickles are so unpleasant to sensitive muzzles that cattle avoid it.

This aggressive, herbaceous perennial (native to Eurasia, not Canada!) has an extensive underground root system, consisting of thick, propagative roots which give rise to more roots (which grow vertically and horizontally), and shoots which pop up seemingly everywhere. They do NOT have rhizomes, and they do NOT have stolons. Apparently, Canada thistle has a unique, hellish morphology allowing it to spread rapidly – 6 meters per year in the U.S. – if not managed (you can read more about this topic here).

Applying plant physiology in the field – literally

But there is a weakness in this aggressive root system – and that weakness is the need for resources provided by the aboveground thistles. The perennial root system stores resources over the winter, then pumps them into new shoots in the spring. This is the chink in the armor – these shoots are USING resources, not providing them, until they slow their own expansion. So the trick is to remove the shoots as soon as they appear, forcing the roots to expend more resources to make more shoots, and so on.

So this is why we are in the field, every day, removing those shoots, systematically clearing areas and then repeating in another week or so as new stems appear. And it’s working. But here is the lesson we are learning that gardeners can apply to their own gardens and landscapes.

Dueling weeders

We have two weeding implements: the “winged weeder” and the “uproot weeder.” The first is my choice, though it is NOT a solely a “stand up tool” for this purpose. My husband prefers the uproot weeder, which twists and pulls out a core of soil along with the root. I don’t like this latter method, as it creates a hole through which sunlight can penetrate, activating both photodormant seeds and stem regrowth. But to each their own.

However, we found another reason that the coring method doesn’t work well: those cores can stay moist and guess what? The stems generate new roots, and left alone could easily re-establish if conditions were cool and moist. Just what we need.

Done properly, this is a quick and effective means of removing the entire root crown of new plantlets

My preferred method, using the winged weeder, is to break the underground stem off as deeply as possible and then work it out as seen int he video. For this you need protective gloves, but not thick ones. You need to be able to feel what you’ve got a hold of.

These gloves are thick enough to protect against most thistle prickles, but thin enough so you can feel what you are holding

Hold onto the base of the thistle gently and as you work the weeder under it move your fingers down BELOW the crown. It feels like a tough bulge and you want to hold onto the smooth stem below it. Otherwise it is likely to break off, leaving the crown viable. You will hear, and possibly feel, a satisfying pop as you dislodge the stem from the underground system. Pull it up carefully. The remaining hole is tiny, and easily covered by pressing on it gently with one’s boot.

My chicken boots close the small holes left by the winged weeder

The advantages to physical removal of perennial weeds

  1. I’m getting out into the fresh air and have lost more weight in the last month than I lost going to the gym in the past year.
  2. I’m controlling a noxious weed population without the use of chemicals.
  3. I’m developing a technique that can be applied to ANY herbaceous perennial in ANY garden or landscape. That’s the great thing about plant physiology – the pattern of resource allocation is not species dependent. Think horsetail and bindweed, for instance.
Our battleground – the enemies are well hidden

Do keep in mind that perennial weeds are perennial problems! We aren’t EVER going to have a thistle-free field, but it will become a more manageable problem as the infestation will have been dramatically reduced this year. I’ll try to do some updates over time.

Tools, tips, and terrible traditions for raised beds – Part 2

Native topsoil – with native rocks.

Last month I started a series on raised bed gardens, focusing on materials and designs. Today I’ll mention some of my favorite tools and materials for putting everything together and getting ready to plant.

Getting your soil ready for raised bed use

Tools and materials: shovel, wheelbarrow, tarp, soil screens

If you’ll recall from my previous post, I like using native soil for raised beds (assuming it is not contaminated with heavy metals or other undesirable chemicals). We have glacial till soil, which means it has a LOT of rocks of various sizes. The bigger ones are easy enough to lift out, but what about all the other ones?

First, realize that SOME rocks are no big deal. In fact, they are important in reducing soil compaction. Finely sieved soil, especially clay soils, will be more prone to compaction than a soil with small pebbles scattered throughout. But the larger rocks are a nuisance.

Small rocks in your raised beds won’t interfere with vegetables but help prevent compaction of heavy soils.

For the first pass through, I have found a plastic crate to work really well. It’s lightweight and the holes are large enough to let soil move through quickly, while retaining larger rocks. I like the milk crate size as it’s easiest to handle. Just set the crate in a wheelbarrow or on a tarp, fill it full of rocky soil, pick it up and shake.

These plastic crates are sturdy and easy enough to lift when filled with soil.

The rocks left in the soil for the most part are easy to work around, and you can always pick out the larger ones as you go (my personal choice). Or if you want to give it another screening, you can build wooden frames with different gauges of hardware cloth, or chicken wire, to remove more of the rocks.

This is a simple soil screen built with 2×4 boards and hardware cloth.

This is a time-consuming process, but the benefit is that you don’t have to top off your beds every year. Your native soil will not be subject to high levels of decomposition and subsidence as will many commercial topsoils with their high organic content.

When you’re ready to fill your beds, be sure to add more soil than you think you will need. It is going to settle, and you may need to add a little more the second year to bring it back to your desired level. But you shouldn’t have to add any more in the future.

Water and time will help soil settle to its final level.

Throughout the soil preparation process, be sure to work when the soil is dry, or no more than just damp. Working wet soil is difficult, and wet soil compacts.

But what about heavy clay soils?

Unless you’ve done a soil texture test, you really don’t know what you have. So before you take another route, make sure you really have a heavy clay soil. If it’s just compacted, then proper mulching will solve that problem too. If it’s truly a heavy clay – let’s say over 40% – then yes, this soil might not be best for a raised bed. In that case, I would suggest finding a different topsoil mix, where clay is no more than 30%. Lay down a membrane to keep this soil separate from your native clay soil. Your raised beds will now function more like giant containers, and you will have to make allowances for drainage along the sides of the beds.

You can estimate how much clay you have in any soil type using this chart.

Your beds are ready – how to keep them that way before planting

Tools and materials: coarse organic mulch, wheelbarrow, mulch fork or shovel, rake, soil temperature probe

A mulch fork will make your life so much easier!

Once your beds are filled, it’s important to get them planted as quickly as possible to prevent continued erosion of that bare, loose soil by wind and rain. If you aren’t immediately planting, then you need to cover the soil with a protective mulch. The only choice you have, if you wish to keep your soil environment hydrated and aerated, is to use a coarse organic mulch. Sheet mulches are not advised since they will interfere with water and air movement. Even if you don’t have plants in the soil, there are microbes and beneficial animals that need a constant influx of oxygen and water. A coarse organic mulch, installed to a depth of at least 4 inches, will facilitate water and air transfer and also keep weed seeds from germinating.

Keep unplanted beds protected with coarse organic mulch.

If you’ve been following my posts over the years, you already know I’m going to recommend using a wood chip mulch. Its benefits to soils and soil life is well established and it is easily moved once it’s time to plant. But you can use pine needles, straw (not hay!), and other coarse organic materials for this purpose. Fine textured organic materials like compost should never be used as a mulch, as thick layers of compost are more restrictive to gas and water movement and also facilitate weed growth. Save compost for a thin topdressing when your soil anywhere on your property is in need of organic matter, and be sure to cover it with woody mulch to keep those weeds out.

This thermometer will help you plant seeds at their optimum time.

While waiting for the right time to plant, consider purchasing a soil thermometer. They are inexpensive and easy to use.  Good publications on growing vegetables will tell you what the soil temperature should be when you plant: planting too early can lead to reduced seedling survival. And while you are waiting you can install a rain gauge nearby, so you can monitor irrigation needs throughout the growing season.

What’s next?

Next time we’ll discuss the dos and don’ts of raised bed maintenance during the growing season and before planting the following year. Most of these practices are adaptable to traditional vegetable gardens, so be sure to check it out!