Hopefully this is a quick question. We're in zone 7a (Virginia) and have had a surprisingly warm fall up until this week. I have relatively new hugelkultur beds with a variety of wood, leaf, soil layers but would very much like to do a cover crop this winter to add some more organic matter and nitrogen to the soil given the newish wood within the mounds will take another year or so to start giving off nitrogen. All that said, is it too late to plant a cover crop in zone 7a and what plants would you recommend that would last well into the fall and/or through the winter. Thanks in advance for any responses!
I used a deer mix as a cover crop on my hugels, mostly clover. I say throw some seed down and see what happens. I'm in 6A and some of the microclimates have gotten down to freezing. If you get some leaf growth it will probably get hammered, if not it will be ready to pop in the spring.
On my zone 7 farm natural seed sprouting is just getting into full mode with the end of the dry season and beginning of fall rains. Areas with dry grass cover do the best because they are protected from drying sun/wind days and brief morning frost. Cutting dry vegetation that has seed heads and covering bare ground is a good way to to get a natural cover crop.
I'm in 6B in southern Missouri, I plant a rye/hariy vetch mix in the fall, and it usually establishes fine if planted now, although much later than this it's more iffy. Last year I had good stands result from early November plantings, but it was very mild last year. In the much colder winter of 2013/2014, some of the young vetch planted toward the end of October didn't make it through the winter, while vetch that was planted in the first half of October made it through okay.
Short version is plant away if you can do it soon. I got mine in just before the last couple rains maybe a week ago, and it is well up, but as long as you can plant real soon and get some rain on it you will be fine.
Best nitrogen producers for the price in this climate for winter I have found are crimson clover -(will reseed if you wait long enough in spring, southern states has inoculated reasonably priced or as a mix), austrian winterpeas (delicious too), and vetch. If you are willing to have it established, I have dutch white clover or landino/medium on hugels depending on the height of the other stuff I am growing, and have caragana, lespezeda bicolor (from the VA state forestry at $0.50), goumi/autumn olive on all hugels as well.