If you scratch the surface enough to get some coverage of the seeds to protect them from the birds, that should be all you need. Wildflowers are used to growing in uncultivated clay soil. Al

I ask the same question, but only for a vegetable garden. How to improve soil tilth without adding unwanted P, for example?

If you improve the soil naturally (i.e without using chemical fertilizers), then it's pretty hard to have TOO MUCH fertility, even for wildflowers and other plants that are notorious for thriving in poor soil.

For most flowers, no-till mulching methods are the best choice. Wildflowers are a bit tricky, though, in the sense that they don't germinate well through mulch. I have the same problem - our builder scraped most of the topsoil off the lot when the house was built, leaving behind very dense subsoil and lots of rocks. Most of our flowers do great, because they have been transplanted into beds that get a fairly steady supply of mulch in the form of compost, chicken manure and pine bark. But those same mulches would prohibit the germination of small-seeded wildflowers. If I simply cast the seeds on top of the hard unimproved soil, then they just wash away in the first rainstorm and/or germinate but never take hold. If I scratch the surface with a rake then broadcast seeds, some of the seeds will find their way into the furrows and a few may germinate, but many will get suffocated when the furrows close back up again.

I think there are 2 ways to get around the problem. One is to treat wildflowers like domestic flowers. Start them in flats and transplant them. This works for most wildflowers, except some such as California Poppies, which grow so quickly that transplanting interrupts their rapid growth cycle. The other method is to simply amend the soil with good organic matter. Buy a few yards of compost and rototill it in, then broadcast your seeds. I wouldn't worry too much about having too much fertility....

-Diggity

If you think about it, when you see a good native stand of wildflowers, you will notice a pretty weak growth of the weeds that often overwhelm wildflowers planted in rich soil. Part of a wildflowers success is its ability to thrive where the competition cannot. Al

Wild flowers and weeds are kind of the same thing depending on how you look at them. In answer to the question any organic material that is low in nutrients like peat will improve soil structure without adding much of anything to fertility.

In reality out where wild flowers grow and Ma Nature is in charge the soil these wild flowers grow in is fairly well mulched (last years flowers died and were layered on the soil) and most likely is more fertile than you think. Where we, humans, have taken charge and used up the humus Ma Nature has carefully provided, by tilling the soil over long periods of time and not putting back organic matter the soils become compacted. Fear not putting some compost or other organic matter on that soil and be sure that in the future all of what grows there stays there to feed the soil in the future.
Peat moss is not a desireable thing to use, especially if it is foreign to the area.

Cultivation opens the soil to increased oxygen and speeds up the microbial action which is consuming the humus in the soil, and results in lower soil fertility over time. Al

I think something that might work well to improve the tilth without increasing the fertility would be to add a lot of peat moss or even sand. Sand and peat moss will break up the soil quite a bit.

Thanks everyone for your suggestions and ideas. I have much to consider between now and next growing season. From what I've managed to research on the internet, wild flower/meadow gardens aren't as easy as simply scattering the seeds and walking away. Of course not! Is anything in getting a garden started ever THAT easy? I haven't found it to be so! Gardeners......gotta admit we are a stubborn lot!

I guess it might depend on what you actually plant there, so the more you could learn about your wildflowers, the better, in case they do really like just what you have there now, but I think you could layer finely shredded leaves, or if you want to buy something, the product often called "soil conditioner," which is pine bark fines, over your area. Over time this would improve soil texture and is not like a coarse mulch , so seeds should germinate; if you don't go overboard and do deep lasagne layers, or do a heavy layer each year, it would still be pretty poor soil.

Why not gypsum? It works for me on my cement soil in NE Illinois. I know it's alkaline but I have to constantly amend with compost to get fertile friable soil.

Westy

Gypsum only works on certain kinds of clay. I believe the clay it helps is called sodic. I can never remember the details; I just remember that it doesn't help my soil.

I agree with Greenthumb in that sand will provide you with the results for soil you are looking for. I tilled in sand by the wheel barrow load for my garden along with wood chips. The garden went from concrete to an excellent clay loam that I am very happy with.
The thing about sand is that it is not going anywhere so once it is done it is done forever.

Coarse sand good.
Fine sand bad.
Gypsum pH 7, neutral.

rangier

Are you planting a wildflower mix? If so tilling will bring up weed seeds and many of those might be difficult to differentiate from your wildflowers.

I would just apply an organic mulch like fall leaves, shredded. Then brush away mulch from small areas, scratch soil surface, and sow the seeds. This will not enhance fertility much at all, but the worms will till the leaves in for you.

Every spring I'm amazed at all the worms and the astounding web of tunnels they plow for me. I never saw this until I started mulching my beds with leaves in fall.

Karen

Thanks everyone for giving me your ideas. I don't know what kind of clay I have. I only know it's gray, compacted and when we are really dry it literally turns into a cement like material.

We bought a shed recently and needed to install those trailer ties to anchor it down. We were trying to dig the holes during a drought. My husband managed to get down about 3 or 4 inches with the post hole digger (remember he was digging these holes right up next to the building so there was no "getting his muscles into it")

After getting that far he got a large screw driver and a hammer and tried chiseling with little success. Finally I got the bright idea to put water in the holes. That helped out a lot.

Yes Karen, I will probably purchase a wildflower mix suited for my area from a reputable source. Since I am the one doing the bulk of the work on this one, I think I will give the leaves a shot. Hauling sand is just more work than this old bod can handle especially since I have 10 cubic yards of mulch to move. Ugh.

Thanks again for all the wonderful suggestions.

Does anything grow there now when it gets watered? If so, you can solarize now, while it's hot, to use up some of the weed-seed bank. I was looking at the Rancho Santa Ana Botanic Garden (Los Angeles area) web site today, and that's how they prepare their wildflower area every year.

Another idea is to start with one or more easy-to-grow wildflowers that will reseed. I planted one 4-inch pot of a wildflower a year ago, in a mulched area, and this year had dozens of plants (in a small area), from which I collected a half-cup of seed (in addition to allowing the birds to eat a lot, and letting a lot fall on the ground).

Perennial wildflower meadows are easier to maintain than annual wildflowers. I've known people who were sure they wanted annuals until they tried it for a year or two, then decided it was too much work -- mostly a couple days at the end of the season, removing the dead stems and shaking out the seeds, so that the suburban front yard would look presentable.

If the soil looses up when wet, you can either wait till it rains, or soak the soil over night. Then scratch the surface, plant the seeds and cover lightly with topsoil or other mulch. That should be enough to at least start the seeds.

Or you can start putting a heavier layer of mulch now, and over a few months the top layer of the clay underneath will become moist and be workable.