Cover Crops: The Easy Way to Improve Your Soil

Twinflower Wilkie and her garden have been growing wild together in Ferry County in northeastern Washington since she arrived there in the 1970s when winters were longer and colder.

She’s married, has three adult children and eight grandchildren, and has retired from a career in advocacy for crime victims and their children. She took the initial WSU Extension Master Gardener training in 2012.

Cover crops help her retain moisture in the soil in her region’s dry climate and provide nutrients while inviting pollinators and other beneficial wild things into her garden. Cover crops also enhance the wild beauty of her garden.

Erin Hoover (02:25)
Twinflower, thanks for joining me today. Welcome to the show.

Twinflower Wilkie (02:29)
I’m glad to be here.

An Introduction to Cover Crops

Erin Hoover (02:32)
So since we’re talking about cover crops today, let’s start off with the basics and talk about what cover crops are and why they’re good for gardeners to use in their gardens.

Twinflower Wilkie (02:42)
Okay, basically when we talk about cover crops, we’re talking about a non-food or a non-cash crop. You’re not using it as your primary goal for that piece of land. Your primary goal might be to grow garlic, for instance, but you’re using the cover crop to nourish the soil, to replenish the soil, to keep moisture in the soil, to keep down weeds.

So, it’s there basically for the soil’s sake, because having good soil will help the main crop to grow well.

A couple of things that come up is what’s the difference between a cover crop and a ground cover. And essentially, a ground cover is a specialized cover crop, but it’s usually a permanent crop. It’s a perennial that’s planted, yes, to suppress weeds, yes, to prevent erosion. But also, as a landscaping feature.

So, a low-lying crop that provides cover. And cover crops usually are annuals which can be either tilled under or mown and provide those same benefits.

How Cover Crops Build and Protect Soil

Erin Hoover (04:33)
So how do cover crops protect the soil and help to build healthy soil?

Twinflower Wilkie (04:40)
Well, one of the reasons we use cover crops is to suppress weeds. It won’t do the total job. You’ll end up with some weeds in your cover crop unless you have an amazingly weed-free soil. But a few weeds among the cover crop, they’re still biomass, so they’re still a usable thing as long as they get mown down or worked in before they go to seed.

You don’t want to let your cover crops go to seed either, any more than you do your weeds. Hairy vetch, for instance, you can find hairy vetch around in landscapes somewhere near a front farm where somebody grew hairy vetch. It likes to go to seed other places. So they can spread and be a nuisance if they are let to go to seed.

So why use cover crops? They add organic matter to the soil, either tilled in or mown down. They often are nitrogen-rich plants.

Vetches, for instance, legumes, field peas, beans, lentils; all of those types of crops have a nitrogen benefit. They break up the compacted soil, especially if you use things like root crops. Daikon radish is popular, sugar beets, mangels, turnips, any of the root crops, or even just something with a long tap root or an expansive root system will break up the soil.

Mustard has recently been found to reduce soil-borne pathogens, so it has a biofumigant property to it. And nematodes and and other unhealthy soil bacteria are negatively affected by it. And moisture retention, of course, especially broadleaf things like buckwheat, will shade the soil, and extensive root systems let the water percolate through the soil effectively and efficiently.

Also, cover crops are used for forage.

And if you happen to have animals, that’s a pretty good return because you feed the forage to the animal, you get the manure, you put the manure on the garden, and you’ve, you know, it’s kind of a double-duty kind of thing.

I didn’t mention beneficial insects, pollinators using cover crops, but that’s another benefit.

Erin Hoover (08:09)
I had buckwheat in one of my raised beds, and the bees just loved that buckwheat.

Twinflower Wilkie (08:21)
Some people even use sunflowers as a cover crop. It’s crazy to think of a cover crop being that large, but it sure does bring in the pollinators.

My husband said he even saw a hummingbird on my sunflowers the other day.

Cover Crop Selection and Timing

Erin Hoover (08:47)
So how do we go about choosing the cover crops we want to use and timing the planting and the management of those crops?

Twinflower Wilkie (08:59)v
There are there are choices that are based on the various things that you want to accomplish. So if you want to add organic matter, the more plant mass there is, the more organic matter there’ll be.

So your tall annual grasses, like oats or rye or a Sudan grass or sorghum, also buckwheat. I have used mustard for organic matter, and today I planted some Red orach, which is a relative of lamb’s quarters. So I guess that’s in the amaranth family, isn’t it? So it has big leaves, and it’ll add a lot of organic matter because it grows really quickly. So all of those are good for adding organic matter. As I mentioned, the nitrogen fixers are the legumes.

Then if you want to break up compacted soil, you’ll use your root crops. And again, most of us as gardeners, those are all good choices because they all have a purpose in managing your crops. As I said, you’re not going to want to let them go to seed, but you do want to let them flower to about the point where they’re half flowering; one-third to one-half is recommended.

So, when you’ve got a one-third to one-half bloom, you’ll have lots of pollinators, and you won’t want to till them under until they’ve at least served the pollinators for a little while. So, your best choice really is a mix of different cover crops together.

Today, after having harvested my garlic – my fall-planted garlic gets harvested during the summer – I put in a cover crop. And I put in peas for nitrogen, radish for breaking up the soil and replenishing some annual rye, some orach for the biomass and…What else did I put in there? I can’t remember. I had a mix of five things.

So, I think that might have been it. And I put that in today. All of those things are hardy to a light frost. So if they’re still in the ground when it frosts, if we have an early frost in September and they’re still in the ground, they will be fine.

Here in eastern Washington, where we do sometimes get some early frosts, I haven’t ever planted buckwheat or crimson clover at this time of year, because they are not frost hardy.

So, if I have a fallow piece of ground, I don’t need it for a main crop. I just want it not to go up to weeds for the summer, and I want to protect the soil from erosion and so forth. I would put in a cover crop of crimson clover and buckwheat in the late spring after the danger of frost has passed.

Then I would work that in in the fall. And then I could plant an annual rye in the fall on that same ground. It will overwinter, as will a lot of the cereal grains. And if you plant it in the late fall, it’ll overwinter and then it’ll germinate in the spring. And you’ll have a very early spring something to protect the soil until planting time. So when I use an early spring cover crop, I’ll follow it with a warm-season crop.

For instance, I wouldn’t bother with an early spring rye where I’m planning to put in peas, because I can plant peas really early in the spring. But if I’m planning to plant cantaloupe or melons or any kind of later spring, early summer crop, then an early spring crop is worth planting.

So really, you know, people say, when do you use cover crops? Really, there are several times that you might use a cover crop.

Like I said, late fall you can even plant your grains your cereal crops over the top of your first snowfall and they’ll just sit there all winter and germinate in the spring. You can’t do that with some of the other crops.

Then in mid-spring you can put a cover crop between rows of your main crop. And for this I would use short greens like say, arugula or cress or the little baby tatsoi, and you can harvest that for greens, but it will still help the soil in between, say a larger crop of broccoli or cauliflower or some such thing. So technically that’s interplanting, but it works as a cover crop as well. Some people call it a living mulch.

So that would be spring, then the summer like, late summer, early fall, after having harvested garlic or some other crop that comes out fairly early, then you can plant a mix of things. I may even experiment this year with planting buckwheat and crimson clover and see how that does as a late summer mulch.

It would get winter killed, and then it would just lie on the ground as a covering; it would still be a protection for the soil. I haven’t done it that way, but I think I might try that. So really there are multiple times in a year that you can use cover crops. Basically any time you have fallow ground.

Erin Hoover (17:07)
Yeah, I was just I just pulled my garlic, and I was thinking about – I have buckwheat – so I was thinking of putting it in there as a cover. Because our first frost is typically late enough that it probably wouldn’t kill until like November.

Twinflower Wilkie (17:21)
Mm-hmm.

Erin Hoover (17:22) So that that’s my hope for this weekend is to go out and plant buckwheat.

Benefits of Cover Crops

So in addition to the soil benefits, what are some of the other benefits of cover crops, say for pollinators or other wildlife in the garden?

Twinflower Wilkie (17:36)
I’m crazy about pollinators. I’m really excited when I see the bumblebees all over the oregano, so of course when they’re flowering the pollinators have food, which is incredibly helpful to them, but it is also cover.

It’s called a cover crop after all. So even though you’ve got a pretty thickly sown area, there is bare ground in between those plants that is then safety. Bumblebees, for instance, nest in the ground, and a lot of the wild bees do.

So there’s some bare soil with a canopy over it, close to the ground but not on the ground. And so they can burrow in there, they can make a nest. Whereas if you use –I’m not against mulches – I’m not at all against mulches, I use those too, but if you use a layer of mulch there, sometimes if it’s thick enough to keep the weeds down, it’s going to also be thick enough to keep bees and butterflies from using it.

Butterflies love getting all the minerals out if there’s a puddle on the earth. So, they like to have a place where they can get to some bare earth. And if there’s a thick enough cover crop that it protects the soil but it allows the butterflies to get down in there and get a drink. They’ll be benefited by that.

Wildlife that Benefit From Cover Crops

Erin Hoover (19:31)
Is there other wildlife that can benefit from cover crops besides like, butterflies and bees?

Twinflower Wilkie (19:36)
I was just thinking about watching a spider. Unfortunately, this spider decided to land on a butterfly and suck the juice out of it right in front of my eyes before I could save the butterfly. But it was, you know, it was there with its web under the leaf of a plant, and down it went onto that butterfly as soon as the butterfly landed.

So yeah, there are others, and spiders are good. We want them. You know, they’re just part of the ecosystem, even if sometimes they get one of my beautiful butterflies.

There are birds. Oh, my garden. Today and yesterday I was watching birds. I just have no words. It was so much fun. I have a mulberry tree. It’s not a cover crop, but it sure brings in the birds.

And then there are the insect eaters, and then there are the seed eaters. And the seed eaters are all over the orach. They love to eat the seeds off of the orach, and the sunflowers are always full of goldfinches. You know, I don’t even care if I get any of the seeds, frankly, from the sunflowers. I just want the goldfinches to eat it.

Erin Hoover (21:04)
The goldfinches and the red-winged blackbirds are all over our sunflowers in the fall.

Twinflower Wilkie (21:10)
It’s also, of course, important to give them a source of water, and the sunflower leaves will catch the rain and hold it, and you’ll see the birds perched on them on the leaves drinking the dew or the rain off of the sunflower leaves.

Wild Home Gardens

Erin Hoover (21:33)
So I understand that you’re a proponent of letting your garden be a little bit wild. Can you tell me what that looks like in your garden?

Twinflower Wilkie (21:44)
Sure.

One thing I’ll have to admit to is that I do a lot of do as I say, not as I do. So sometimes I intend to get things under control, and they don’t it doesn’t happen.

And so one of the things that I always try to keep a little bit of lawn and our gas-powered mower quit, and our electric mower quit, and so the lawn mower I have now really only mows a little bit of lawn. It’s a manual push mower, and I don’t do as much manual pushing as it would take to mow the whole lawn.

So one area just went wild, and so it’s coming up with oregano, yarrow, grass, some that is going to seed, which some of the butterflies really like, and it’s just full of bees and especially bumblebees, and they love the oregano. I’ve had oregano going wild for many years actually because I noticed that the bumblebees liked it. So I don’t harvest at all, and it goes to seed, and they come up, and I put in bouquets.

Some people want their flowers to stay in one place and be just the ones they planted, and they’ll pull out all the extras, the volunteers. But I love the volunteers, and my garden is overrun with poppies and sunflowers and oregano and all kinds of things that have gone to seed.

Maybe they’re weeds. They’re plants that came up where I didn’t plant them. So are they weeds? Well, I love them. So I advocate for letting things go wild. The orchard is pretty much a ground cover of strawberry plants, clover, and self-sowing flowers. And it keeps the moisture in, it lets the bees and the butterflies have a place to go, and smells nice.

Erin Hoover (24:26)
Yeah, between the oregano and the strawberries in my food forest area, I’ve just let go. And I don’t even get any strawberries because they’re so dense, but the insects really like it, so I’m just letting it be.

Twinflower Wilkie (24:44)
Mm, I’m glad to hear it. Woman after my own heart, obviously.

Simple Ways to Get Started with Cover Crops

Erin Hoover (24:51)
So what are some simple ways gardeners can get started with cover crops maybe this summer or this fall?

Twinflower Wilkie (24:58)
I have to put in a word for Rainier Seeds. If you’re in eastern Washington, it’s going to be a local source for you. It’s in Spokane. And they have a lot of mixes. And so, the simplest way to start is to get a mix. They market to farmers, and so farmers aren’t going to pay retail prices; they pay wholesale prices, so it tends to be less expensive.

You can start with probably 25 pounds of seed, but it’ll last. You can keep it in a garbage can with a tight lid. A seed mix should be good for four or five years and give you that whole range of types of seed so that it will fill that range of needs that gardens have.

You can also get cover crop mixes from True Seed Market or Johnny’s Seeds. I like Rainier partly because it’s local and partly because it’s less expensive. You’ll also probably have nearby garden centers that sell seed mixes if you want a smaller amount.

So I would start with a seed mix as the simplest way to get started and probably the best way because, you know, unless you’re targeting some specific problem, a mix is a good way to get a rounded crop.

And then what I did today to plant my mix, I just worked it up with my spading fork, watered it, and I didn’t like turn the soil or anything; I just broke it up because you want your seed to make good contact with the earth. Then I broadcast my seed, and I put a very light layer of fine wood shavings as a mulch over the top just to kind of hold it down, hold in the moisture until it gets a chance, and then sprinkle it again.

If you are doing a no-till method of gardening, then how you terminate your crop makes a difference. So I had bare soil because I had just pulled out the garlic, and so all that was left was the mulch around the garlic. And so it was basically bare.

If you’ve just grown a cover crop, and you want to plant through that cover crop, you’ll knock the cover crop down. You’ll either roll it or mow it or even stomp it down.

Then what I would do is I’d take your spading fork or a broad fork if you have a broad fork and kind of punch into the soil so that you have places to seed where it will fall into the soil. Because if you just broadcast over the top of a bed where you’ve flattened your last crop, a cover crop, the seed won’t reach the ground, and it won’t germinate. So, you’re going to need to at least work it into the soil there the way and you would do a no-till.

Either that or you can terminate that cover crop by working it into the soil through tillage. If you have planted something that has a really good root system that’s going to that’s really breaking up your soil for you and ending your soil compaction problems.

No-till is just a terrific way to let those roots keep doing their job even after you’re terminating the above-ground part of the crop. You’re not terminating the below-ground part of the crop; it’s still doing its work.

Erin Hoover (29:35)
So for us, because we have raised beds and they’re no-till, we tend to lack nitrogen. So I like to do nitrogen-building covers. But I like last fall, I did a vetch, and then I terminated it in the spring, actually with the string trimmer, a weed eater. So just to cut it really close to the ground and then just let it lay to start to decompose. And then I would just like create little opening you know, push it apart so I could put like a start in the ground after it had been sitting there for a few weeks. That seemed to work pretty well.

Twinflower Wilkie (30:13)
Yeah, that’s it; that’s exactly it.

Final Thoughts About Cover Crops

Erin Hoover (30:16)
All right, is there anything else you’d like to add about cover crops?

Twinflower Wilkie (30:19)
I think what I say about every kind of gardening, which is the way to get started, is get started. And the way to learn is to fail sometimes. Like this spring, I had decided that I was going to use mangels on a certain area in my garden. I was going to let it be fallow.

Mangels are a type of beet that grows a root that’s like a couple of feet long, they say. I don’t know; I haven’t pulled any of them yet. But I apparently must not have watered them enough. I don’t know exactly why, but it didn’t germinate well. And so there are mangels one every three or four feet, and nothing in between.

There are dill and poppies and calendula, etc. It’s not a bed of mangels. It’s kind of pretty. It might produce something; I’m not sure. I may get a crop of mangels, or maybe I’ll just try something different next year.

So I’ve been gardening here since 1987. I certainly don’t consider myself to be an expert on cover crops yet. I’m just trying things out and sharing what works. And sometimes something doesn’t quite do what I expected. But that’s okay too. It’s learning.

Erin Hoover (32:08)
My learning experience was with Phacelia, which is this beautiful purple flower that’s an early spring cover crop.

Twinflower Wilkie (32:15)
Mm-hmm.

Erin Hoover (32:16)
And that’s how I learned the hard way to terminate your crop before it’s in full bloom. Because that stuff spreads like wildfire. It was everywhere for years.

Twinflower Wilkie (32:32)
Which is not a terrible thing. I have feverfew and feverfew is kind of like that. Once you’ve got it, you’ve got it. And if you don’t, you know, do something with it before it goes to seed, you’re going to have it another year.

And like I say, sometimes our gardens go a little bit wild, and maybe that’s all right.

Erin Hoover (32:59)
All right, then we’ll wrap it up. Thank you so much for being here, Twinflower. This was great. I learned a lot about cover crops.

Twinflower Wilkie (33:07)
Good. I’m glad I was able to say something helpful. I hope people enjoy it.