Cotinus obovatus (American Smoketree), Maackia amurensis (Amur maackia), Ostrya virginiana (American Hophornbeam), Corylus colurna (Turkish Filbert), Sorbus alnifolia (Korean Mountainash). The first four are more tolerant of dry conditions. If your soil is reasonably moist then the Mountain Ash might be worth consideration. It has nice flowers, attractive fruit, and terrific fall color. Bob

That's a Magnolia grandiflora, native to the American southeast all the way into Oklahoma. It's struggling in the alkaline soil and the heat: I've seen them in Virginia and they are much deeper green with larger leaves. http://en.wikipedia.org/wiki/Magnolia_grandiflora The pink-flowered ones (species and varieties) are native to areas with climates that are too different from ours: some are tropical and can's survive our winter freezes, others are from the cooler damp foothills in SE Asia and will survive the winters but can't stand our hot dry seasons. They need a deep, acid soil and a high humidity ... we don't have that. Bauhinia can usually survive as a lawn tree, and it has pink cultivars.

I've found that one of the biggest problems planting under a crape myrtle is their dense root systems. What size is your tree? Does it provide some shade to the area in the middle of the day? If it does that will open the area up to a wider variety of plants. Some plants you could try are native wild petunias (Ruellia caroliniensis), sun loving bromeliads, native false garlic (Nothoscordum bivalve), rain lilies, blue plumbago, crinums, and native monarda (Monarda punctata). All of these are plants that I have growing under my tree crape myrtle. Only half of the bed is watered by the irrigation system, the other half relies primarily on the rain.

Full sun intensity is about 1928 PPFD at noon today here in Pittsburgh (about 41N latitude). Near tropic of cancer where sun is overhead now it is about 2026 PPFD. PPFD is a measure of number of photons striking an unit area. Most full sun plants will reach photo-saturation at about 1000-1200 PPFD. That is they cannot process anymore photons beyond that. Leaves are adapted to that, especially the outer leaves of a tree. Essentially, the variation in full sun intensity with location is not important. Saturation is not a problem for plants - leaf temperature is. Leaves have to spend energy to keep themselves cool so that they can photosynthesize. As temperature rises the net gain from photosynthesis becomes smaller as the leaves try to keep cool. Beyond 90F the leaves start to shutdown and it starts with the outer leaves to save energy while protecting the inner leaves. In fact, the enzymes responsible for photosynthesis become ineffective at this temperature. So leaves are just spending energy to keep cool. At even higher temperatures, especially if it is also accompanied by dry air, the leaves will die. Dry air increases transpiration demands and thus more wasted energy. Sacrificing leaves under these conditions is a natural response. The scalded leaves will still be attached to protect the inner canopy unless a storm takes them away. That exposes the inner leaves, that are not as well adapted, to the full brunt of sun. Either these leaves will quickly adapt or subject to photo-oxidation. Photo oxidation will also look like leaf burn but this time the plant often reacts by dropping the leaves. In tropics, this will induce summer dormancy. Container growing is far more stressful to plants since roots are also subjected to higher temperature and limited availability of water. Beyond 90F the roots ability to absorb nutrients and transport is compromised. Roots will focus on absorbing water only. But that will increase the concentration of nutrients in the soil - especially if using chemical fertilizers - and cause even more stress for the roots. A long way of saying most plants will benefit from some shade when temperatures are high. Mid day watering is also good under these conditions.