Southwest Desert Flora

The Simaroubaceae or Quassia family of flowering plants is a small family with less than 20 genera. Plants are mostly tropical and subtropical.

In North America than are approximately 11 genera with 30 accepted taxa overall. Arizona has two well known species; Ailanthus altissima, tree of heaven and Castela emoryi, Crucifixion Thorn. The Plant List describes 19 plant genera and 121 accepted species names.

Plants here are trees or shrubs, mostly dioecious; leaves; deciduous, alternate, rarely opposite, leaves pinnately-compound or simple; "inflorescence" panicles or raceme; flowers solitary; "fruits" a capsule, drupe or samara.

The family is known for medicinal plants and species used for furniture and flooring. The popular Tree-of-Heaven, Ailanthus altissima and Amargo, Quassia amara from South America are both well known. Amargo or Bitter-ash, Quassia amara, has properties for uses as an insecticide and food additive as well. Bitter-ash also contains compounds which include quassin, a bitter extract used as additives in soft drinks. Quassin is one of the most bitter substances found in nature and is 50 times more bitter than quinine.

In this family, one of the best known species with a cosmopolitan distribution is the Tree-of-Heaven, Ailanthus altissima. Here in the southwestern United States, Tree-of-Heaven, Ailanthus altissima is invasive and listed in New Mexico as a "noxious weed". Two other well known genera in the family include the tropical Quassia and Simarouba.