The University of Arizona Herbarium has approximately 2000 works in its illustration collection, including works on permanent loan. The scientific illustrations in the collection have been reproduced in scientific publications describing plants native to the Sonoran Desert Region including Agaves of Continental North America, Arizona Weeds, Trees and Shrubs of the Southwestern Deserts, Livestock Poisoning Plants of Arizona, Grasses of the Southwestern United States, Cacti of Arizona, Flora of the Gran Desierto and Rio Colorado of Northwestern Mexico, Plants That Poison, and The Trees of Sonora, Mexico.

Also in the collection are a number of watercolors and pastels by Ella Howard Estill done in the early 1900s. Although these are not “scientific illustrations” they represent her intention to naturalistically render common plants of the Sonoran Desert.

Many of the illustrations continue to be used in contemporary scientific texts and journals and in field guides. The entire collection documents plants native to this region, and as such is of great importance. Over the past five years in cooperation with the Herbarium staff, The Sonoran Desert Florilegium Program has organized and archived this collection.