Help me choose a cover crop...

Raleigh, NC

I am familiar with using cover crops, but not sure what to use in this situation. I recently tilled and amended several large areas of pure clay. Right now I am slowly planting the 'bones' of the bed i.e. permanent trees and shrubs, but these are very small, young plants and I want to fill in all the open spaces with a cover crop that will choke out weeds and assist with amending the clay and building up quality soil to a greater depth.

I need something that will not reseed, if possible, as it will be difficult to use a tiller anymore, so all turning over of the cover crop will be by hand to avoid damaging the already planted items. Also would be great if it also looked attractive as this area is about 50% of my backyard. Upper South climate, part sun, part shade. Any suggestions?

San Antonio, TX(Zone 8b)

Personally, I would be inclined to go with an attractive mulch, at least until your small plants have gained some size and their roots have had a chance to anchor themselves. Almost any cover crop will compete with young root systems and will also try to reproduce itself by forming seeds. A mulch with small size pieces will break down faster than the large bark types. It will not incorporate into the clay without an annual turning under by hand, but can be scratched into the surface without disturbing the roots of the permanent plants. Depending on the soil's pH, you could consider rice hulls or grass clippings that are well chopped. Mulch will maintain a more even moisture content and temperature level during summers - important for plants that are still shallow rooted. Yuska

Raleigh, NC

I do plan to mulch also, but was hoping for a cover crop that would help with the clay, too. Hoping to grow it for 4 months or so, turn under, then mulch before the hottest weather in August. I have mulched all that I planted, so I don't think a cover crop will compete too much, but not sure. Anyone else have an opinion on this? Should I can the cover crop idea? The one negative is that its a LARGE area, and I've already used all this years leaves etc (and my mower is a mulching mower, so no grass clippings). Buying mulch would be a little pricey....especially as if I put it down now, I will probably have to redo it in the fall also. Thanks!

Vienna, ON(Zone 5b)

Just dropped in and noticed your post.

I use winter rye for a cover crop. Its massive roots will help break your clay. It grows very quickly and you'll have a huge amount of organic matter to till under. It is a perennial, so you may need to pull some persistent ones by hand after you spade it under. You may find it attractive--basically it looks like grass. In four months it'll be about a foot tall I imagine, given your climate. Although it's a cool-weather plant it is extremely drought resistant. One caveat-- it is very difficult to turn it by hand. The stuff is so heavy with roots that it's a real backache of a job.

Southern Mountains, GA(Zone 6b)

How about some buckwheat? It's an annual, very attractive, makes loads of nectar for bees , smells fantastic and isn't too big a chore to mow and turn under.

Raleigh, NC

I'm thinking, i'm thinking...Thanks guys! One question--can I plant both of these now, not in the fall, and if so, when should I turn it under? If I can plant it now, then I would hope to turn it under late summer for fall planting. Will these germinate in warmer weather, or only cool? I'm only familiar with planting these in the fall, but I'm assuming both will germintate and grow fine in warmer weather...

Southern Mountains, GA(Zone 6b)

Now is the perfect time for buckwheat, I hope you'll try some.

Vienna, ON(Zone 5b)

I've used buckwheat as well as rye. I don't know if the buckwheat would have the guts to deal with your clay. The roots are small clumps-- they don't descend like the rye does. I don't know how either of them will behave in warm zones like yours. I've never let my rye grow through the summer-- if I don't turn it under in the early spring it just gets too heavy to manage without a tiller. I don't know if it will go dormant in heat. I've planted buckwheat in mid-summer (just to cover a newly dug bed that I intended to plant the following spring) and knocked it down in September. Buckwheat should be turned under just before it flowers, so you maximize the "nutritional" benefit for the soil.

Adrian, MO(Zone 6a)

why plant a cover crop? you mean like clover to fixate nitrogen? what will you ultimately want to plant there? and why not just plant it? I believe even most annuals can reseed themselves so anything you plant is going to come back if it isn't chocked out by something else, probably weeds. are you going to be planting some type of grass to buffer and fill in between your other plantings? if so why not plant it?
The only plants that actually break down clay soil are dead ones, they add organic matter otherwise plants usually use more nutrients than it gives back, unless you're counting leaves, fruit clippings etc. usually farmers use covercrops to protect the soil from erosion and to preserve moisture in the soil etc., but they also rotate their crops so that one plant doesn't completely rob the soil of certain minerals.etc. they can go longer between fertilizing. I don't see any benefits of a "cover"crop in home landscaping, but I very well could be wrong!

Vienna, ON(Zone 5b)

A cover crop is more appropriately called "green manure" since it is meant to be turned under and it's OM added to the soil.

If you read the original post, yotedog wants to plant a cover crop to improve clay soil and keep weeds down during the process. For a perennial bed, this is an excellent idea, IMO. With perennials you're better off spending the time preparing and improving the soil-- once your plants are in, you're really limited to working in the gaps.

Another thought on the choice of cover crop plant-- buckwheat will be less effective at weed suppression than other plants.

San Francisco Bay Ar, CA(Zone 9b)

We used the Soil Builder Mix from Peaceful Valley Farm Supply on the adobe clay soil in our garden. It did a wonderful job of loosening the clay to where we no longer need a jackhammer to make a planting hole in summer, and it doesn't suck your shoes off in the wet season. I've been very impressed with that cover crop mix.

http://www.groworganic.com/item_SCM120_SoilBuilderMixRawLb.html


Their catalogue has a wealth of info on cover crops as well.

Raleigh, NC

Great thread--lots of input...I'm still researching all your suggestions...Garden Mermaid, it looks like I can't plant the Soil Builder Mix this time of year, though. Yes, I know, I should have done all this last fall.......! As a last resort I might seed some really tough annual, then go with the clay busting cover crop this fall. I would really like to plant this fall though, so still looking for the perfect answer....

San Francisco Bay Ar, CA(Zone 9b)

Why can't you plant it this time of year? Is that due to your weather?

Raleigh, NC

Well its very hot and humid here starting soon, and I know some of these are cool weather germination type plants. Thats why I'm asking for input--I'm not sure which will grow this time of year. The problem I'm having is that most people only want cover crops in the fall and winter, so there isn't much info out there about trying to grow them through a very hot summer..as usual, I'm doing everything backwards! But my experience has been that in the gardening world you can often get away with doing it all wrong because Mother Nature just fixes everything...!

San Francisco Bay Ar, CA(Zone 9b)

Buckwheat does well in the heat. It doesn't take the cold well.
That being said, we planted soil builder mix on a perimeter bed in July or August last year and it did fine through the searing 100' heat wave.

If you have the space, you might try planting several plots of different cover crops and note how the crop does and how your soil responds.

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