"Species range from drought-resistant shrubs such as creosote bush Larrea tridentata and prickly pear Opuntia spp., sotol Dasilyrion wheeleri and Agave spp. to walnut Juglans spp., hackberry Celtis spp., oak Quercus spp. and soapberry trees Sapindus spp. in the richer soil of the canyons."