Adding Fertility: Sow a Winter Cover Crop

Although our winter garden is in full swing, we nevertheless do not have every single bed planted out with cool-season vegetables. That's because it's important, if you can, to put some of your garden beds into a rotational cover-cropping program. A cover crop, or green manure, is a plant sown not for eating but to enrich the soil. Instead of taking nutrients OUT of your garden, they actually add them back. They also act to improve the soil's structure and it's ability to sustain growth and hold water and nutrients.

There are many types of cover crops, from legumes which grab the nitrogen out of the air and infuse it into the soil, to buckwheat, which serves to choke out invasive weeds before they take over your garden. The choice of a proper and productive cover crop for your garden firstly depends on the time of year you are sowing it. Some green manures won't germinate if it's too cold, while others can handle frost, even snow, with no problem. Secondly, you should consider whether you've got a special agenda over and above a basic desire for adding soil fertility.

For my California garden that gets plenty of frosts, but no snow, I had a larger choice of crops that would survive the winter here. Knowing that, I then sought to figure out what other benefits besides improving my soil health I could gain out of a specific cover crop.  After a bit of research, I settled on Pacific Gold Mustard.  I've got a few dodgy pests in my soil, and this type of mustard supposedly deters both wire worms and harmful nematodes.  The fact that David Kinch can also use the delicious spicy young leaves in his signature "Into the Vegetable Garden" dish, also played into my decision.

For a 50 square foot bed, we use about half a cup of seed.  The bed is not prepared at all, just cleared of previous vegetation.  We sprinkle the seed uniformly on top of the soil, trying to achieve about two or three seeds per square inch.  We then scratch it into the top inch of soil with a hard metal rake.  It's better to use an up and down motion rather than an actual raking movement.  If you rake back and forth, you're more likely to get bare patches where you've raked the seed out of place.  We then make sure the bed is kept constantly moist until germination occurs.  This usually means we've got to water every day if it doesn't rain.  The seeds can begin to emerge 48 hours after sowing, if the weather is mild.  If not, expect to wait a week before you see any green.

Once up, back off on the water, only giving it a spritz during extremely dry conditions.  You can begin to eat the tender greens within a few weeks by either pulling up the whole plant or by snipping off individual leaves.  It's best to mow down the whole lot before it flowers and sets seed, though.   We will cut all of the mustard off at the soil level in about late February, turn it all under the soil with our spade forks, and let it naturally compost for a month or two before we plant our warm-loving veggies.

So a triple threat: soil health, pest control, and yummy eats!

Comments

[Love Apple Farms]

Maria, if your garden is in a mild climate with no frosts, I would give it a try. In mid winter, getting the seed to germinate in the cold ground is the biggest challenge.

[Maria Sayare]

Hi there - Just wondering is it too late to plant a legume cover crop in mid december?

Thanks much,
Maria

[Gardeners Belfast]

Hi.

Just dropping in from Belfast to say Hello and I hope that you had a great Thanksgiving.

Excellent crisp clear photographs by the way. It's great to see you making inroads into the Gourmet Magazine too. Well done!

[Nate]

I normally do fava beans as a winter cover crop. I even let some of them go to pod so we can eat them.

Are there cover crop seed mixes which incorporate mustard?

[Matron]

I can highly recommend any legumes for their nitrogen fixing nodules. It really does work - I make sure I leave the roots and nodules in the soil over Winter.

[Laura (in los gatos)]

Wow, your hoop house is awesome.

I've had trouble with mustard escaping, because I tend to get lazy about turning it under (guilty expression). I like legumes for cover crops.