You might think about the shorter zinnia...I love the tall cactus ones the best but the short series are very pretty. I have good luck with mini snaodragons here they form nice tight clumps in pretty colors.

Madagascar periwinkle, commonly called vinca, if you pinch the growing tip they will form little bushy mounds nicely. They also have a very dark glossy green leaf. Dwarf zinnia is what I planted in my sunny hot/dry border-

Calendula and small zinnias...maybe hot pink zinnias?

I suppose I should have mentioned that I also use Lilliput and Thumbelina zinnias in the beds too as they are terrific bee magnets here at the sanctuary.

Has anyone had experience with 'perennial mounding monarda' that someone told me about?