Root patterns and hydrogeomorphic niches of riparian plants in the American Southwest

► Root depth data was compiled for 125 riparian plant species of southwestern USA. ► Root depth varied with plant moisture affinity, growth habit, and flowering season. ► Hydroriparian herbaceous plants had shallowest roots; xeric shrubs had deepest roots. ► Introduced species had deeper roots, suggesting adaptation for drier riparian conditions. ► For many riparian species of southwestern USA, rooting depth remains unknown.