If both perennials and annuals have failed due to soil, it is time to amend the soil. Heavy clay will be cold and wet in the spring, hard and dry in the summer. Amending with organic material and mulching will improve the soil thus allowing plants to grow. So called "Wildflower" mixes usually contain a mixure of full sun perennials and annuals so likely will not do well. The listing from American Meadow contains a lot of sun lovers and not many of them are going to like heavy clay.

You will need about 6 inches of compost and 3-4 inches of mulch spread over your bed to amend it. You have about 600 square feet of bed, so need about 300 cubic feet or 10 cubic yards of amending material: that's a truckload. It may be a bit costly, but cheaper than losing hundreds of dollars of plants every year.

So, now or in the spring (soil should be dry), order 10 cubic yards of compost, 5 cubic yards of mulch and rent a rototiller. Spread the compost over the bed and till it in. Then spread the mulch over the bed. Some people like to amend clay with some coarse sand as well. If you use sand, subsitute it for about 25% of the compost, ie use 2 yards sand and 8 yards compost.

The mulch will break down over time and thus continue to add organic matter to your soil. You will need to top up the mulch every two to three years.

Next, take a good look at how much shade you have. If it is dappled all day and dense some of the day due to trees overhead, choose part shade, full shade or woodland plants, do not choose full sun or part sun plants.

If you want the American meadow mix, seed it in before the mulch goes on. Or buy perennials and plant after the mulch goes on.

Here is a link that might be useful: Amending Clay Soil

Thank you. One more question....

I really do not want to rototill the area. The one year we did you wouldn't believe the weeds it stirred up. This year I tried the no-till method and chopped most of the existing weeds with the hoe in Spring. Amazingingly, there are very few weeds right now and I'd like to try to keep it that way. However, we do mulch with at least 3-4 inches of organic materials each year so hopefully it's sinking in a little.

What about the so-called "claybuster" seed mixes. I'm not sure I want to buy them because they are pricey but I was thinking I could get some of the seeds and make my own mix. I re-evaluated the area and a good portion of it (the front) gets sun until about 2 pm. Deeper in the back there isn't much. Goutweed thrives back there ;)

Here is a link that might be useful: claybuster seed mix

I am not a fan of Wildflower Farms, because many of their mixes include non-native and invasive junk. But I looked at the claybuster mix and it has a lot of high-quality native species. Nothing in there that I wouldn't recommend. You could pick and choose small quantities of these species to make your own mix, but I think that $90 for a quarter pound of this mix would be a good investment.

The key to the success of any seeding is site preparation. I agree that rototilling is an invitation for trouble -- it will stir up buried weed seeds and will create a perfect seed bed for new weeds. If you have kept your site weed-free for a while, you can seed the area this fall/winter and expect success. (But ideally, I would recommend treating with roundup repeatedly trhough a growing season before seeding). Amending soils is rarely needed for native perennials, as long as you select the right mix of species for your conditions.

If I was trying to grow wildflowers in this relatively small area I'd probably start with plants for most species, and seeds of only a couple species. Scatter seeds of a few very easilt grow plants to get the ground covered and discourage weeds and to provide some first-year color, then little by little add in other plants. You should decide how you want to treat the area before deciding of you want to amend the soil. If you want to treat the area like a wildflower "garden" where you'll pull weeds, perhaps mulch, and generally put a little time into maintenance, then you can amend the soil. However, if you prefer to make this area semi-wild and not put too much time into maintenance, then don't amend the soil. Digging up the soil and adding oragnic matter will make plants grow better, faster, larger, but it will also greatly encourage weeds. On the other hand, a lean, unamended soil is better if you want to put minimal time into maintenance. Yes, wildflowers will grow slower in poor soil than they would in amended soil, but weeds will also grow slower, and the effect will be more pronounced in weeds, so on balance you'll have more wildflowers and smaller, fewer weeds if you don't amend the soil.

I'd scatter seeds of Clasping coneflower (Rudbeckia amplexicaulis), Black eyed Susan (Rudbeckia hirta), a grass such as little bluestem, and only a couple others if there is something you particularly like. I'd probably place plants (instead of seeds) of other species, especially plants that spread vegetatively such as Wild Bergamot (Mondarda fistulosa) and Mountain Mints (Pycnanthemum species). I"d add Nodding Onion (Allium cernuum) and Butterflyweed (Asclepias tuberosa), although butterflyweed also grows easily from seed. I'd add a wild sunflower to the back of the border (Helianthus divaricatus, H. microcephalus, etc.) because I like them. I'd expect asters and goldenrods to show up on their own, or collect them locally. This time of the year you should easily find wild sunflowers, and soon asters and goldenrods blooming all over the place. It shouldn't be too hard to find a clump you like, get permission from the bewildered land owner who won't understand why you want some of his weeds, and divide the clump, taking a small rooted portion and leaving the rest. This way you'll get a nice local plant without disturbing the wild population too much. My rule is that anything hardy enough to form a healthly clump on a roadside will easily recover from me taking a small piece.

There are other ways to go about starting a wildflower planting, but thats what i'd do.

If you don't want to till, you can try layering the soil with compost or other organic matter and letting the worms do the tilling. However, if you have really heavy clay and you previously planted semi sun/ semi shade plants and they all died, then you may have no choice but to amend the soil.

With sun only until 2pm at the front of the bed and heavier shade at the back, you will need to chose woodland edge native plants or semi shade garden plants. Have you thought about using understory shrubs like dogwood to transition from the trees, then use a few woodland edge plants like coralbells at the front.

William Cullina of the New England Wildflower Society has two good books, one on Wildflowers, one on trees and shrubs that you should look for in your library. He has lists of plants for various conditions and great tips on each plant. You would need to check the "plants for clay" list against the "plants for shade" list and use plants that make both lists. Personally, I would use plants not seeds with tough conditions.

I did find this list on the web, again, you will have to select the semi shade/ shade plants.

Here is a link that might be useful: Clay Plants

Try Prairie Moon Nursery, and Prairie Nursery, I believe that one of them has a clay buster mix, also.

www.prairiemoon.com
www.prairienursery.com
www.ionexchange.com
www.newfs.org

And also the LadyBird Johnson Wildflower Center, whose website addy I can't remember off the top of my head, but you can google it. April

And absolutely do not add sand to your soil...there isn't enough sand in the desert to correct the problem.

If you add sand to your soil what you are going to get is cement.

Don't Rototill...invitation for lots and lots of weeds to sprout! I learned the hard way, LOL!

Thanks to everyone for your help. I decided to go with a number of plants from the "claybuster seed mix" but I ordered the seeds individually from Easywildflowers.com. They were much less expensive that way and John was very helpful. I got the seeds in two days! Anyway, now all I have to do is rake, scatter, and wait to see what happens. Wish me luck...

It's always great fun in the spring waiting for what you've seeded to show up! Best of luck to you! April

sand and clay are what they made the pyramids out of. dont ever add sand to clay soils.

and based on the information that u gave, ie that things died because of the soils...

u only have 500sqft roughly, that isnt such a big area that it would be expensive to invest in a mulch or a soil building program. i agree that 10 yrd of cheap mulch is more than enough to do what needs to be done.

lasagna gardening is an option. i think it would be to everyones benefit to research this topic.
another solution to this problem is putting a 3" layer of mulch on in the fall and letting nature do her work over the winter. then in the spring, plugging in plants.

or a combo package of the two. add a layer of newspaper and waste material. then putting on 3" of mulch over the top. in 1 year, you will be amazed how improved ur soil is. in 3 years of constant watering and adding mulch as needed, u will hardly recognize ur soil structure.

i know that soil isnt the most exciting thing but the fact is, its the most important. u may be fine if u just rake in some seeds of hardy spp. but if i had to guess, based on experences with clay, u wont be. or more importanly, u wont be satisfied with the results.

and i have perminately gotten rid of my roto-tillers. there is nothing there for me anymore.

my suggestion is to improve what u have and plant later.

froggy

I have found that it is better to work with what you have rather than to fight it.
find the right plants for that area.
some short native grasses like little bluestem and prairie dropseed might be just the thing interspersed with a mix of local forbs,

The great thing about choosing native plants is that they don't need any soil amendments... good luck and I hope that your plants do well.