To amend clay soil you want to add gypsum and or sand plus of course as much compost as you can make. This will give you a very rich soil. And you should do a soil test and add the amount of lime or sulpher needed for the types of plants you want to have.

I have a clay slope so can't really change it with out having it all fall down on me. So far I have had luck with the following plants.

Gladiolus, Dusty Millers (although they grow slowly), chives, green onions, shallots, and yellow onions, Thyme, par-cel (this is a hybrid between celery and parsley, Miniature snapdragons, peonies, miniature roses, daffodils and crocuses and portulaca.

I have had bad luck with calendula, pinks, carnations, ipomposis, chinese lanterns, honesty, chinese houses, rosemary (I always have trouble with rosemary), babies breath and that's about all I can remember at this moment.

Plants that survive but don't thrive: Columbine, love lies bleeding, hosta, balsam, tomatoes, and bell peppers.

For the plants that don't do well in the clay I've started planting in raised beds and containers that I put on the retaining wall that holds the slope in place up to a point anyway. I hope some of this information will help you.

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tkhooper, that par-cel sounds very nice. I also live in virginia with the heavy red clay soil and would like to try some of that out in my new Garden. I dont recall seeing that variety in my Gurneys or Burpee catalogs. Is it uncommon? Can you advise where you obtained yours?

tiff, the hydrangea needs lots of water - if your not getting rain, i'd water it every couple of days. especially the newest one - you want to get it's root system established as soon as possible. give a good soak and water the soil around the plant as well - you want the roots to stretch out. if you only water at the base of the bush, the roots won't have far to go to search for water.

how bad is the clay? i've got it too, it's not too bad tho...there's a good couple of feet of good soil on top of it, so i've not done much for amending.

all my plants have done well. roses, hydrangea, peony, iris, daylily, gladiola, purple cone flower, vinca, clematis, lilac. i've also got chive and i plant tomatoes and peppers every once in a while too. my tomato plants ALWAYS do well.