|I know that chameleon plants can be invasive, especially in moist soil, however I was wondering how they would cope in hard dry clay. Would they still grow?|
|In my experience this plant will grow in drier soils, however it may not have that lush carpet-like effect that it has in moist soil and especially in moist, rich soil. Then in an unusally wet year, it will suddenly take off and can get out of control.
For clay based soils, you may want to work in a generous amount of organic matter along with a small amount of fine grit or sand to try to loosen the soil prior to planting. This will help whatever you plant to become established. Clay based soil is usually somewhat heavy and poorly drained, but once it dries out it becomes hard and is difficult to rewet. The organic matter helps greatly with this problem, and any watering should be done slowly/gently so it can percolate through.
Some plants you might consider in a sunny area would include rudbeckia, echinacea, sedum, hemerocallis, and asters for instance. In a shadier area you might look at Vinca minor or epimedium. All of them are quite drought tolerant once established and can make a nice groundcover but will need some watering during the first season while they become established.
Your local professional nursery staff and/or county extension may also have some suggestions based on a more detailed understanding of the site and your design goals.