In New Mexico, landscape trees don't exactly have it made in the shade. Sunny, dry conditions make it hard for some trees to survive, limiting homeowners' options. Currently, we have a limited palette of shade trees for southern New Mexico. St. Hilaire is trying to identify shade trees that can best handle moderate drought conditions, which can be caused by more than lack of water.
Trees growing in pots or in the city surrounded by lots of concrete also have trouble surviving.
In an initial greenhouse study, St. Hilaire worked with graduate student Coye Balok to identify drought-tolerant trees that could thrive for years to come. Balok took measurements for four months, watering the trees and allowing them to lose half of their water to simulate drought. The leaves can tell a lot about which trees can weather New Mexico's weather. Typically, thicker, waxier and hairier leaves mean less water loss. To analyze these leaf characteristics, Balok and St. Hilaire studied scanning electron and light microscope images of the seven species.