What to do with cover crops in raised beds.

When I started using cover crops in the home garden, I couldn't find much information about what to do after they had grown. In hindsight it all seems obvious but there was too much information out there, largely intended for farmers. This is actually very easy stuff.

Fall-planted cover crop grown in a raised bed.

First, don't think like a farmer or even a market gardener. Farmers have tractors. Farmers can let the cover crop grow until just before it is going to go to seed, then do some combination of rolling it down, mowing it, and/or tilling it into the soil. Big equipment makes that feasible. Market gardeners also have tools to smash cover crops down and then cover them long enough to kill them and get the residue decomposing. Us home gardeners have to do this by hand so it needs to be attainable and simple. We need to kill the crop while it is still manageable and we need to make sure it actually dies.

So, say you planted a fall cover crop blend in a raised bed. Time permitting, you want to allow it to grow up to the point that is about to flower or start setting seed. If you need the bed before then, give yourself 2-4 weeks for the crop to break down. I will terminate crops anywhere between February and late spring, just depending. Above, in the raised bed, I fall-planted blend of rye, peas, vetch. and clover. I am still cutting big wads of this to feed to my chickens and don't need this bed until late-May, so I am going to leave this for another three weeks. Below, I have an in-ground bed planted with oats and clover. I will want this bed sooner rather than later, so I am terminating the cover crop now.

A cover crop of oats and clover in a home garden.

You'll want a trusty hand hoe, hori hori knife, or anything that lets you easily dig the roots up. Then, exactly like you were removing weed, just slide the blade under the roots and lift the plant right out of the ground. Then (and this bit is important!), do your best to incorporate the whole plant back into the soil. Pretend you are a teeny weeny plow. Smoosh it down, grab a few loose handfuls, and try to get some soil contact on it. Helen Atthowe does a great job in her book, The Ecological Farm, explaining that cover crops need to be mixed into the soil surface to prevent nutrients from volatilizing into the atmosphere. You did all the work getting your cover crops to grow; don't let all that precious nitrogen just leak away into the air!

In a couple more weeks, come back for a second pass. Because you turned the plants under the soil, some of them will have tried to reroot and will still be alive. Just repeat the process and that should finish them off. Shortly after that, you should have a very nice seed bed to plant into. One final thought: don't let your cover crops go to seed! If they are allowed to self-sow, they will quickly become foe instead of friend, especially the grasses. As soon as they have grown enough mass to improve your soil, thank them for their service and put that biomass to work. That's it! Pat yourself on the back; you grew your own fertilizer!

The cover crop is gently turned into the soil, creating contact between soil microbes and plant material. This helps limit losses of nitrogen into the atmosphere.