Reader Question - Cover Crops

Did you know that you can email me directly if you go to the ‘contact me’ page on this website? I would absolutely LOVE to answer any question you have, and if I can’t answer it, I’ll be honest about that, too. It’s all too obvious that I am running out of things to write about. When I was taking Horticulture classes, I was always learning something new about gardening, or trying experiments out in the lab, and I had lots of information to share. Then I swerved briefly into more general science classes, which still had some good, relatable info. But now I’m fully into my upper division courses, which are all for my Environmental Studies degree and include boring things like data collection and carrying capacities and population control and clean energy. Well, they aren’t boring to me, but they certainly aren’t the focus of this blog, and aren’t as fun to read about as bugs and vegetables and flowers. So I really appreciate questions! They give me a chance to write about fun things and to question my knowledge and opinions of them and of course, that way we can all learn together, which is my favorite thing of all.

This morning I got a wonderful email from a reader named Jill, who lives not far from me: “ I sadly lost most of my garden due to the heatwave and an irrigation issue. I’m looking at cover crops and know nothing about the subject. Do you have any tips or links to places you buy the seeds from. Maybe some simple do’s and dont’s? “ Thank you Jill! Thank you for reading the blog and thank you for this question and thank you for your faith that I can answer it!

Buckwheat, a summer cover crop in warm climates

Cover crops can seem intimidating and confusing, so let’s start from the beginning. What is a cover crop? The simple answer is that a cover crop can be anything you want it to be. The Oxford Dictionary definition is “any crop grown for the protection and enrichment of the soil.” Farmers tend to use specific plants to satisfy specific requirements, which can be very important, especially if you want to grow without inputs i.e. chemical fertilizers. Some plants provide nitrogen, some phosphorus; others attract beneficial insects, and still others provide biomass for feeding animals. Some are grown during the summer, and some are grown during the winter. Some are grown after a specific cash crop, to replenish certain nutrients.

If you’re a farmer, and you’re making a living growing and selling your crops, you’re going to want to know a lot more details about cover crops and how they can be used to save you money. But if you’re a regular home gardener, your needs are different. You want something to improve the soil, attract beneficial insects, look pretty, and feed your compost pile when it’s done growing. Maybe you want to avoid buying soil amendments this year (they’re going to be hard to find, considering how many people are gardening for the first time). Maybe you don’t like the structure of your soil, and you want to improve its water-holding capacities. Maybe you like birds, and you want to feed insects that will in turn become food for the birds. These are all fine reasons to grow a cover crop.

The thing that is most important is that you have a living root in the ground at all times. Now, if you live in upstate NY, you know that eventually that root will likely die, and that’s the way it’s supposed to be, and maybe even you time a crop so that it winter-kills and you don’t have to cut it down yourself. If you live in California, however, you can grow different cover crops at different times of the year, year-round. Having a living root in the ground is what improves your soil. The plant harvests sunlight, makes sugars, and pumps those sugars down into the roots and into the soil. This attracts microbiota, tiny creatures that feed on the sugars that the plant provides. In turn, they poop, providing micro-manure to the soil, and they burrow, improving air flow to the roots, and they die, recycling nutrients, and they move a ton of soil, making it rich and crumbly and perfect. If there’s no root in the soil feeding the microbes, then they move on or die off (or become very, very sluggish, waiting for the next influx of food). It’s not the plant that is feeding the soil, it’s the animals that are feeding the soil - the bacteria, fungi, protozoa, and nematodes - the primary and secondary consumers. When you spread manure or compost on the soil, it doesn’t feed the plant - it feeds the soil life, which in turn form these associations with the plant roots and provide the nutrients the plant needs to thrive.

image credit: center for food safety

So if you look at it this way, any plant can be a cover crop. No matter what kind of plant it is, it is going to continuously pump sugars into the soil and feed soil life, therefore improving your growing medium.

However, some plants need a lot of nutrients. If you’re planning a summer garden full of squash or melons, for instance, you might want a high nutrient load in the soil before you plant them. Why not grow a crop that will also add specific nutrients to the soil? Here is a handy chart, provided by the Organic Growers School, to help you determine which crop you need at which time.

image credit: the Organic Growers School

Don’t worry too much about the seeding rate. I just spread it on thickly, and that does the trick.

I’ve grown many different specific cover crops, and I tend to stick to two - crimson clover in the winter, and buckwheat in the summer. Some years I don’t use them at all. Some years I plant them intercropped with other plants that I am using for food. Some years I grow them alone in specific beds. They’re both great, but both require cutting and removing before they set seed (at least here in CA), or else they will seed everywhere (which is not the worst thing in the word). I’ve also done several mixes, especially in summer, that combine many species to provide many different nutrients. This is actually proving to be best for the soil, generally. If a living root in the ground is good for the soil life, then a wide diversity of roots in the ground would naturally be even better. I’ve also grown winter wheat and oats, which provided me with the best variety of beneficial insects I’ve ever seen in my garden. Long grass is apparently second only to a pond for attracting wildlife, and we saw that firsthand.

Many seed houses sell cover crops, but the best place I’ve found is Walnut Creek Seeds in Walnut Creek, Ohio (I know, it’s a coincidence that my town is also named Walnut Creek). They’re super-friendly, the farmer (Dave Brandt) has pivoted his business from growing corn and soy to growing cover crops, and he is also involved in a lot of research with the NRCS to show how cover crops can save money for traditional farmers, improving crops, soil, water levels, and erosion. Their prices are incredibly reasonable. They also sell specific gardening mixes for the home grower. I’ve used both the summer and the winter mix, and can vouch for them. Mr. Brandt is also one of the first conventional farmers to help develop special seeding equipment to enable farmers to plant their cash crop directly into the residue from a cover crop. He has a lot of videos on his website, and I think they are fascinating. (I have also ordered phacelia from them, by the pound, for early spring seeding in my pollinator gardens. The bees go crazy for it.)

If you’re interested in how soil can be a huge catalyst to improving our planet (and some history on how it’s disappearance has contributed to societal failure), an excellent book is Growing a Revolution: Bringing our Soil Back to Life, by David R. Montgomery. If you’re looking for a nice film to help you understand these concepts, look for Symphony of the Soil, which came out years ago and is still one of the best films about soil I’ve ever seen. For a crash course on soil health and how cover crops can be used to improve your land, you can’t do better than Living Web Farms’ series with Roy Archuleta and Dave Brandt - these videos will blow your mind.

If I were Jill, and my garden had been decimated by heat and smoke (mine is pretty sad too, sister!), and if I wasn’t planning on winter food crops, and I wanted to improve the soil, I would plant buckwheat right now. It’ll grow and flower quickly in our late summer/early autumn heat; it’s quite a pretty plant, with lovely tiny white flowers. Around late October or early November, I would cut it down and lay it on top of the soil where it grew. This will provide cover for the soil over the winter. (Studies have shown that it’s better for the soil if you just lay the residue on the top, rather than turning it under.) Or, you can add that residue to your compost pile. I would then plant either a winter mix of grain, clover, peas, and radish (or the mix Dave sells) right into those same beds, and let it grow a bit before the real winter hits us. When it begins to warm up again in January/February, that cover will take off and grow like mad, and you can let it go until you are ready to cut it down and plant your spring crops. This will do wonders for your soil, and you will also be feeding pollinators: Both now, with the buckwheat, when it’s hot and crispy outside and there’s not a lot to eat, and early in spring, when the bugs are emerging from their winter dens and need nutrition, pronto.

Do any of you use cover crops regularly? What’s your experience with them? Do you have any tips for Jill (and the rest of us)? If so, please leave a comment down below. Good luck, Jill! Let me know if you have any more questions.

Soldier Beetles

Since I let all the brassicas bloom (that is, the cabbage, kale, mustard, broccoli, and cauliflower), I’ve been seeing a lot of beneficial insects in the garden. My kale is riddled with cabbage aphids, and I knew it wouldn’t be long before the predators started showing up.

Soldier beetles (or more accurately, leatherwing beetles) are an insect you want to invite into your garden. Less than an inch in length, and brightly colored (like a soldier wearing a uniform, hence the common name), these carnivorous bugs overwinter in leaf litter and debris, and lay their eggs in the soil. The larvae hatch underneath the soil and eat the tiny bugs they find there. As adults, they roam plants looking for eggs, or caterpillars, or aphids. They do not damage plant material. They will eat pollen and nectar, which also makes them excellent pollinators.

Soldier beetles (Pacificanthia consors) look a lot like lightening bugs, but they do not have light-producing organs. When I put this picture up on iNaturalist (and, are you a member yet? It’s such a great citizen-science site!), someone identified it as a Downy Leatherwing Beetle. Researching them online is difficult because they haven’t been studied extensively. I did find some advice on how to attract them to your garden: Choose flowers that bloom over a long season. Provide water, as they are known to frequent moist habitats. Provide undisturbed, mulched soil in which to pupate. Include permanent perennials in your planting scheme to help keep that area undisturbed. Do not till, but rather add organic matter to the top of your soil (good all-around advice, anyway). And let me know if you see them in your garden!

Here’s another beauty I found flitting about in the chard, today. A Painted Lady! I haven’t seen a painted lady (Vanessa cardui) in my garden in a long time. And it’s early in the season for butterflies. Favorite host food for the caterpillars includes hollyhocks (I’ve got those), legumes (I’ve got those), and thistles (the nearby open space has got those). I’m delighted to see this beautiful butterfly and hope this means I can look forward to lots more in the summer to come!

Tweaking the Tomatoes

I’m doing several different experiments with the tomato crop this year. I just can’t help myself. Each year I try something new and each year I learn something. Meanwhile we always get a ton of tomatoes, so it doesn’t hurt my bottom line. And I want to get ever more efficient at growing this crop.

I’ve got about 60 tomatoes and 20 hot peppers out in the ‘greenhouse’ at the moment, and another tray of about 20 more tomatoes and 20 more peppers under lights in my bedroom. The ones in the greenhouse are doing fine. We have nice sunny days, and I open the door of the greenhouse in the middle part of the day (if I’m home) and allow the plants to get beautiful solar radiation, then close it up about 3 pm and let the greenhouse heat up inside before chilly night comes (between 45-49 degrees outside generally, but much, much warmer in the greenhouse). So that is one experiment - I wanted to see if I could minimize the time and space that seedlings take up in the house (our house is so tiny, even one table full of seedlings is in the way), and I think this is working. Since I don’t intend on putting tomatoes in the ground until the nights are solidly above 50 degrees, we’ve got a while. Also the soil is still fairly cool. I’m hoping not to pot them up further, just plop them into the ground when conditions are right.

The tomatoes will go on the south side of the garden this year, in six raised beds. Two of the beds are 4x4 and four are 4x8. This limits me to 40 tomatoes. Eight cherry tomato plants (4 in each) will go in the 4x4s. 16 each of paste and slicers will go in the remaining 4x8s (8 in each). And this planting is where some other experiments are going to come in.

I was not pleased with the health and production of my cherry tomatoes last year. I pruned them to a single stem, the same way I did all the others, and it severely limited our crop. We love to have the cherries for fresh eating and quick salads, and we really missed having a lot of them. They are also generally the first to ripen in June, which bridges the gap for us until July when the bigger guys are ready to eat. I’ve done some research, and there is some evidence that pruning cherry tomatoes really limits production. So I’m not going to prune them this year. Tom will make a sort of wooden cage to hold them all upright and contained, and we’ll let them go wild.

I’ll still prune the bigger tomatoes to a single stem. However that leaves the soil quite bare, and I don’t have homemade straw this year (I didn’t grow wheat or oats this winter), so at first I was just thinking about how I could creatively mulch the ground around them. And then I was like, wait, why am I not just planting other plants to fill in that space? I mean, I intercrop everything else (grow various types of crops together, or a crop with a cover crop, etc). Why not tomatoes? So I did a little research on that topic, too. There’s not a lot of real science about growing other crops with tomatoes. I think farmers don’t do it much because tomatoes need a lot of air and light to avoid disease; that’s why we prune them in the first place, to remove vegetation to provide more air and light. And that’s super important in a humid location. But - not so much here in summer-dry California where all irrigation is applied at the drip line. I remove those extra branches for a different reason - because I want fruit, not leaves! And bigger fruit at that! So why not replace those bottom branches with a different plant, one that shades the soil, crowds out weeds, retains moisture, and feeds soil life? As long as the plants have a different kind of root system, they shouldn’t compete too much. And I’m not talking about, like, companion plants or something. Companion planting is a nice idea but not exactly science. I’m talking intercropping. Getting two crops out of the same space. Or, even cover cropping, which simply improves the soil.

So I’m going to try it. Basil is a natural to put with tomatoes - it has a shallow root system, it likes the same amount of water and heat and light; it stays smaller than tomatoes; it has a beautiful flower that attracts beneficial insects; and it’s something we eat a lot of. I could do basil alone and that would work great. But diversity is good, so how about adding some cilantro to that? It’ll bolt and re-seed; it adds a new kind of flower for those beneficials; it can be eaten (and we do eat a lot of it); and it looks beautiful. So I could mix those two herbs. I could even mix in a third thing, like cosmos? Purely ornamental, but beautiful and beneficial too. Or I could intercrop buckwheat? That improves the soil and provides a flower for good insects. Or I could mix them all up?

I haven’t figured out the particulars just yet, but I’m definitely going to try this method. Have any of you intercropped or cover cropped your tomatoes? If so, please let me know how it went for you!

The Benefits of Wasps

Many years ago, Kate attended a local summer Girl Scout camp, which took place in a secluded canyon in Briones Regional Wilderness, which spans four cities and is a haven for wildlife. One of the highlights of this camp was that the girls learned how to cook lunch over a campfire, and did this (with the leaders' help) every day. We're not talking hot dogs and hamburgers; we're talking cast iron dutch ovens on coals, and using box ovens, to cook everything from taco casserole to potato and bacon hash. Dessert always followed; cake or cobbler, with ice cream made in hand-cranked buckets, natch. It was fun. Messy and a little dangerous, but fun. There was one major problem every year, and this was yellow jackets. The tiny beasties would swarm the picnic tables in droves. Everything had to be constantly covered. Girls, aged 5-15, screamed repeatedly. There was always a group of them running down or up a canyon, screeching about the 'bees.' 

My job at this camp was nature leader, so, me being me, I did a lot of research about the yellow jackets and incorporated some of what I learned into the lessons, hoping to calm fears. For instance: Did you know that yellow jackets are one of nature's best garbage collectors and composters? Without them, we'd be knee-deep in detritus. Yellow jackets also eat insect pests that bother us and eat our crops, like flies and caterpillars. I often find them, in the heat of summer, scavenging dying bees from the 'graveyard' under my hive. They take those back to their nests and feed them to their young. Yellow jackets even pollinate flowers, like in the photo above, something I never knew before today. I watched this lady long enough to take the picture and fire it off to my insect professor, who wrote back immediately: "Yes indeed, they love pollen and any sweet liquid like nectar!" It's hard to hate anything that pollinates flowers.

The problem, of course, is that they are so aggressive. They get into our food when we try to eat outside. They drop into soda cans, surprising the drinker on the next sip. They can sting repeatedly without any repercussions. It's so freaking annoying. I hate them hovering around the chickens, eating any tidbits I put out for them. If the yellow jackets nest in your yard, they are very hard to eradicate. As my dad found out, last summer, in his own yard, they are not deterred by any kind of bee suit and will sting through them with abandon if their home is threatened.

Yellow jackets are social creatures, just like bees, and in fact are in the same family as honeybees and ants (Hymenoptera). The queens, newly hatched in fall, overwinter in leaf litter. In the spring, they emerge and find a place to start a nest. They eat until they are strong enough to start laying eggs. This is happening right now, here in CA. A yellow jacket trap placed outside now might just catch queens, and prevent a hoard of worker wasps over the summer. The only one I've found that works is this one.

Image credit: PestWorld

Another wasp that we often find around our homes and gardens is the Paper Wasp. These tend to make their nests under overhanging eaves. I have a group that nests every year in the shallow eaves under Adam's train shed. Paper wasps are great pollinators, but their true benefit comes from the fact that they are very efficient hunters of caterpillars, beetle larvae, and flies. They attack them and take them back to their nests to feed their young. They are aggressive if bothered, but mostly just stay to themselves. They don't care about our picnic dinners, which means they are very polite guests in the home garden.

Image credit: Bugguide.net

Then there are all the myriad kinds of predatory wasps, most of which you'll never see, which parasitize caterpillars. This means they lay their eggs in the body of the caterpillar, which then hatch and consume the caterpillar from the inside out. Yuck, and cool!

So the next time you see a wasp of any kind in the garden, instead of freaking out, try to focus on the fact that they perform an important service for us. I'm not saying not to kill them; my patience is often tried to the limit with yellow jackets. But just give it some thought before automatically switching into 'destroy' mode. 

Syrphid Flies

This beautiful creature is a Syrphid Fly, also called Hover or Flower Fly. I found her on one of my Gaillardia plants a few weeks ago. I'm so excited that there are Syrphid Flies in my garden because they are so beneficial!

Syrphid Flies (of which there are many) mimic honeybees and wasps as a defensive camouflage; they do not sting, but want bigger predators to think they might. The adult flies are fabulous pollinators, eating both nectar and pollen. The larvae of some types are voracious predators of aphids, which is probably why I found this one in my garden. The eggs hatch and develop into larvae which eat a lot of aphids - in fact there are three larval instars (or phases) of some kinds of Syrphid Flies. I don't know about you, but I'm seeing way more aphids than I usually do, so anything that can help me control them is terrific! I'm hoping this fly laid lots of eggs on my aphid-ridden blanket flower. 

There are also Syrphid Flies that develop in stagnant ponds and eat decaying organic matter while in the larval instars. They form unique larvae called 'rat-tailed maggot.' The rat tail is a siphon that allows the larvae to breathe while in water. I first heard about this kind of hover fly from a professor in the UK that I like to follow - he has great books - and a great You Tube channel with lots of interesting pollinators. I'm not sure this kind of fly lives here, but I made his 'hover fly lagoon' anyway, to see what comes of it. It's quite easy - you just need a container filled with water and organic matter.

I went begging my neighbor for some of his long, weedy grass to use in this lagoon, since Dr. Goulson says this is the best kind of organic matter to use. I'll let it fester (I put it a long way from the back door!) and see what grows there in a few months. Should be interesting. One thing I'll need to do is check the water level frequently and watch that it doesn't dry out. I'll keep you posted!

Again, though, aphids will bring in the kind I took a picture of above. So you don't need to do anything except STOP USING PESTICIDES. Nature sends in predators when prey develops. And if you use pesticides (chemical or organic), you'll kill the good guys along with the bad. So far this year in my garden, the aphids have brought in: lady beetles, green lacewings, snakeflies, predatory mites, and syrphid flies. Plus probably others I haven't even noticed yet!

Here is the video from Dr. Goulson about this project. His books are worth reading, as well, if you have interest in native bees.