Since you are almost there, you could spend the extra $ and get favas (Banner, at Territorial Seeds for example). They are almost certainly the best cover crop for you bar none. First, they fix much more N than any other legume (triple what beans do), so come next spring you will only need to add some wood ash for P and K. Second, they have a deep taproot, and because they grow six feet tall, I am sure they will go down at least a couple of feet.
Obviously, they will produce enormous amounts of organic matter. They specialize in clay soils, do poorly in sandy soils, do poorly in heat, they are hardy to 10F, and tolerate waterlogged conditions.

The drawbacks are the cost (the seed is quite large, so it costs money) and also I am uncertain about the planting time. Favas really are the perfect winter cover for zones 8-9, going October-April and providing food and fodder besides all those goodies above. In your case, you may have to try in September, and if they die, try again in February. In Michigan, Zone 6, I plant under cover in February (for food). Cut them in May and plant immediately.

glib - thanks for that. I'll do some research on the best time to plant favas in this area.

glib: What does it mean when you say "plant under cover"? I live in MN where it is terrible cold. Do you know if it is viable cover crop here in an open garden, say fall or early spring?

I mean I plant in a hoophouse. Surely it is viable even if the favas die. You will still get organic matter, just less. In MN they will die, of course. Perhaps in your case it is best to use oats or clover? Oats are usually planted knowing that they will be cold killed. They cost less and are more adaptable. Less roots but still a lot of above ground matter. Anyhow, look at those companies who have cover crops for the home gardener, and see what they have. Do you need biomass, N, or deep soil breaking?

Hoophouse - Duh! Under cover made my mind wander.

I've been thinking of using a cover crop mostly because weeds grow before and after frost. Something is gonna grow, assuming it should be with benefits. And I do believe my soil is mostly hard clay (is there soft clay?) and compostables. I have researched it for my area, but only ended up with information overload and forgot why I was searching.

I apologize to iamtrying if I'm overunnig his/her question with my own.

Steve, that sounds like a good idea! I thank you for "making a decision for me"! :) I'm going to give that one a try. Much appreciated!

Definetly trying to throw everything at it I can to remedy the clay situation. Understanding the best route to take is several seasons of adding compost. Soil tests ok for most everything EXCEPT organic matter. Starting just this year so hoping to get there ASAP, as mother nature will allow. A tilled-up, neglected lawn is not what anyone refers to as an "Ideal" garden bed.

It sounds like your first beds are overly amended to the point that roots wouldn't want to leave the bed and spread into the clay. This is a very real phenomenon. It can also act like a bathtub in heavy rains. Roots and water move best through uniform soil.

I'd mix 1/2 the amendments from your first beds into your new ones and put ome clay from your new ones into your old ones.

I too have very hard clay, but my garden beds are rich and friable due to years of composting and NOT walking on the beds!!! Ammended clay WILL NOT simply re-compact itself when the root dies. When I fork up a big hunk of clay in spring, there are channels all through it left by roots, worms, bugs, etc. It's wonderfully crumbly.

My dog trampled lawn on the other hand... you could make pottery with the clay if you can dig in it.

iamtrying

Hello from a northern MN Lori! I have terrible compact clay. I do have some clover I grow in the back, but it's just to attract bees.

I have tried gardening just in my soil, with some sandy loam and composted cow manure. Nada luck.

This year my dear hubby built me a raised 4' x 12' concrete block garden. I went with Mel Bartholemew's Square Foot Gardening method and mix.

Unbelievable! My peas are almost 7 feet tall! My broccoli was wonderful. Everything else grows like crazy too!

For those of us in cold climates, with short growing seasons, I would recommend the Square Foot Gardening method as the only way to go!

If your interest is mainly in making the soil easier to work, you might also try adding a very thick layer of mulch.
Last summer, I moved into a rental with hard compacted clay. I saved all my lawn clippings and spread them about 6 inches thick where I had planned to have my garden this year. I decided to have a bigger garden. The difference between working the soil that had been mulched and the soil next to it was amazing. The soil under the mulch sliced like butter up to 18 inches deep. The stuff right next to it that had not been mulched required a pick axe to get deeper than 6 inches.

Since you asked about cover crops;hubby tills his veggie bed in fall after the crops are out ,then scatters winter rye seed over it all and waters it in.......it stays green all winter ,,,then he tills it in for spring planting.He calls it green manure.Has anyone else done this?

Winter rye is inexpensive, germinates quickly and makes it through a cold winter. It's great stuff. BUT, be sure and till it in when still green, do not let it go reporductive and form grain heads. At that point it can be difficult to till it in. Tom

Re Making Hard clay soil workable . One good cover crop is tiller radish (diakon) You plant in fall at least 60 - 90 days before a hard frost . The roots will grow down up to 2 feet and die with the frost , they reduce compaction, and provide organic matter and quickly rot . You need to add nitrogen to promote their rapid growth. Another thing you can do is add powdered gypsum ,wet down and till in fine pinebark. There is also a liquid gypsum you can apply with a hose end sprayer . When you till clay soil it is necessary to have the right amount of water to keep from damaging soil structure. Any kind or free organic matter helps you can use powered charcoal , used coffee or tea grounds , any type of manure , mulch , sawdust compost , leaf much , after tilling or amending soil add about 4 inches of mulch such as tree chipper mulch, grass clippings or leaves. Within 1 year soil should be workable . As far as rocks, they will surface every time you till , just set them aside and after a while the amount of rocks will decrease . As far as tilling hard clay wait for after a hard rain and bust soil with railroad pick or garden tiller and it will be slow going the first time . If you take a handful of soil and make it into a ball ,and throw onto a hard surface it should crack a little but not turn to dust . Do not try to till when too wet or too dry . Another trick is to get a 2 foot long drill bit in hammer drill and drill holes in fall and fill with water , when water in holes freeze it will help to soften soil . Some crops such as carrots and beets are better grown in raised beds until soil becomes more workable .