Answer: There are a hundred great choices! I'll suggest a few of my favorites.
Lantana can take the hot southern sun and keep blooming until frost. It is now available in many shades of yellow, orange, red, coral-pink and a mixture of these. Gold Mound, Patriot Rainbow and Patriot Firewagon are three that should stay within your height range.
Petunias are getting back to their roots! Look for the old reseeding cottage garden types which are regaining popularity. The 'Purple Wave' and others in the 'Wave' series will do quite well through the heat of summer if you provide plenty of water.
Portulaca and purslane offers a very low growing (about 3") option for hot dry areas. Zinnia linnearis with its 1" orange or white flowers laughs at the hot summer sun. And don't forget vinca, another proven summer color annual.
Burpee carries seeds for many of these plants and your local garden centers will likely offer many in transplant form.
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