What the Cottonwood Knows

Along the dry creek beds of eastern Colorado, where summer temperatures routinely hit triple digits and the soil cracks into puzzle-piece patterns, the cottonwood trees have no business being green. Yet every August, while surrounding grasses go brittle and brown, the cottonwoods remain lush and full. Botanists call them phreatophytes — deep drinkers. Their roots don't spread wide across the surface searching anxiously for moisture.…