My feed stores have some in season. I generally go with a winter rye for the weed control and organic matter. All my paths are seeded in white common clover for nitrogen contribution.

Determine what you want to improve and go with the best suited cover crop. Some are deep rooting to break up hardpan or clay. Fresh organic matter is good but generally delays spring seeding for a couple of weeks as it decomposes sufficiently to avoid effecting germination; draws on soil nitrogen and may reduce germination.

Here is a link that might be useful: Overview of Cover Crops and Green Manures

The cheapest place to buy small amounts of cover crop seed is the grocery store, especially the Whole Foods type. You can find raw buckwheat (not kasha), wheat berries, barley, rye berries, soup peas (whole not split), black eyed peas, dried favas and garbanzos (or any bean for that matter), flax seed, maybe even fenugreek or mustard in the bulk spice section. Renee's garden also sells packets of buckwheat and other cover crops that I've seen in the vegetable rack at the regular garden center or, of course, on-line. Larger quantities can be purchased by mail from Peaceful Valley.

Also, if you see end of season vegetable seed market down at Home Depot or something, buy a handful of packets of mustard greens or daikon radish. You need to seed cover crops pretty thickly, so that would be the priciest option.

Feed stores generally sell grain that is not cleaned sufficiently to be used to plant crops. Feed store grain will contain weed seeds.

I get my cover crop seeds from a farmer's supply store and specialty seed company.

Some times the places that sell fertilizer to farmers will have seed. Or they will know where farmers buy their seed.

I buy grass seed directly from the grass seed farmer. I have to purchase a 50 pound bag, but it is only 30 cents a pound, and the germination rate is excellent. You really can't argue about that.

Picking a cover crop if you want the N to be available is very important, too.

If you just want the organic matter and erosion/weed control it's easier and broad in choices.

Just to use organicdan as an example...he's far north in a cool climate with a short-ish summer crop growing season (at least compared to me in NC). His plantings of winter wheat when incorporated makes it's N available pretty quickly. This comes in very handy for those that need to cram their summer growing season in quickly because it ends early.

If someone in my area was planning to do something like plant winter wheat to grow a corn crop that won't be planted/grown until weeks after harvest of the winter wheat it's N availability would be vastly deteriorated by the time the corn was in it's best growth stages.

Ultimately, though, the organic matter and erosion control are a lot more important than N availability for most home gardeners. It matters a lot more for people planting field acreage where they manage every $ of their field inputs.

I've tried both winter wheat and rye grass. IMO, WW was about 100 times better! The ryegrass roots did not die as easily and the foliage was not as good (I use a weed-eater to mow it at ground level in early May, then rotary till the ground several times before planting the garden. WW is a bit harder to find in the Cincinnati area but there is a Feed Store a few miles up the road where I get it - 65� per pound. Twenty pounds, sowed thickly, covers about 1000 sq. ft.

Mike

I've used feed oats from the elevator here in town for 5 straight years now and have never had a problem with weed seed in with the oats.

Here is my method:
1) till 1-2" deep.
2) from about Sept. 15th - 30th plant with Gardenway planter about 1 1/2" deep in rows about 8 - 12" apart
3) water in with lawn sprinkler
4) watch it grow like wild till the hard frosts kill it.

The narrower row spacings are for the later planting time in my area. It is amazing but, planting 2 weeks later than the 15th leads to much less top growth by the time the frost kills it and the row middles are not completely covered if 12" spacing is used. If I use 8" spacings and plant on the 15th, the crop is really crowded and there is an increasing risk that the killing frosts will not do their job leaving me with the task of weed whacking it to keep mature seed heads from forming. Mature seed heads would just leave me with a bunch of oat weeds the following Spring and more work getting rid of them.

When done well in the Fall, a lot of leftover N in the soil gets pulled up into the tops and the tops die off leaving a thick layer to over winter. In the Spring, the cool season annuals don't germinate in the cold soil and dense shade under the mat. By the time I'm ready to plant the warm season crops where the oats were, the soil is warmed up and the mat has broken down to a large extent leaving a soil with very nice tilth. Give it a whirl!

It's sort of funny that I use oats here in the middle of wheat country instead of wheat. Some of the old timers have commented that they used to plant oats as a cover crop after seeing my garden around this time of year, nobody does anymore. A few farmers plant a few acres of turnips and then graze cattle on the tops in the Fall.