Carnegiea gigantea, Giant Saguaro

Southwest Desert Flora

Home to the plants of the Sonoran, Chihuahuan and Mojave Deserts

Cirsium ochrocentrum, Yellowspine Thistle

Euphorbiaceae, Spurge or Euphorbias Family

The Euphorbiaceae or Spurge and sometimes Euphorbias Family consist of forbs/herbs although tropical species may be shrubs or trees. Some tropical species resemble certain members of the Cactaceae Family and are often confused with them. Most of the Euphorbs are native to the tropics however many are non-tropical species such as those found in Arizona and the United States. Once again showing Arizona's varied habitats that includes the northern most distribution of several tropical species.

Leaves are mostly alternate although many in Arizona are opposite and have stipules subtending the leaves. An interesting characteristic is that most of the leaves are simple, but compound leaves are always palmate and never pinnate.

Plants are monecious or dioecious and flower configuration is extremely variable. The arrangements and shape of the stipules may be a key characteristic especially in Chamaesyce. Also in the genus Chamaesyce, and other Euphorbs, is a cyathium which is a specialized pseudanthia ("false flower").

The Euphorbiaceae Family has 228 plant genera with over 6,547 accepted species named. The Plant List includes a further 4,634 scientific plant names of infraspecific rank for the family Euphorbiaceae.

The Plant List also now includes all but 1 species of the former genus Chamaesyce placed now within the genus Euphorbia which now includes 2,046 accepted species. The Plant List includes a further 1,707 scientific plant names of infraspecific rank for the genus Euphorbia.

There are several hundred species of the Euphorbiaceae family in Arizona, the largest genera include Chamaesyce and Euphorbia.

For Chamaesyce, there are over 90 species in the United States, Canada and Mexico. World-wide over 440 species and there are approximately 39 species in Arizona.

For Euphorbia, there are over 21 species in the Southwestern United States: Arizona has of genus Euphorbia, California has 25 species, Nevada has 6 species, New Mexico has 22 species, Texas has 31 species, Utah has 12 species. All data is approximate and subject to taxonomic changes.

References:, updated 08/07/2019
U.S. Dept. of Agriculture, Natural Resources Conservation Service on-line database and USGS ITIS search - (accessed 06/19/2019 )
https://plants.usda.gov/java/stateSearch
The Plant List (2013). Version 1.1. Published on the Internet; http://www.theplantlist.org/ (accessed 06/23/2019).
http://www.plantlist.org/1.1/browse/A/Euphorbiaceae/
The Plant List (2013). Version 1.1. Published on the Internet; http://www.theplantlist.org/ (accessed 06/23/2019).
http://www.plantlist.org/1.1/browse/A/Euphorbiaceae/Euphorbia/
Wikipedia contributors, 'Euphorbiaceae', Wikipedia, The Free Encyclopedia, 10 June 2019, 17:38 UTC, https://en.wikipedia.org/w/index.php?title=Euphorbiaceae&oldid=901255686 [accessed 23 June 2019]
Wikipedia contributors, 'Cyathium', Wikipedia, The Free Encyclopedia, 9 April 2018, 13:53 UTC, https://en.wikipedia.org/w/index.php?title=Cyathium&oldid=835567826 [accessed 23 June 2019]
U.S. Dept. of Agriculture, Natural Resources Conservation Service on-line database – ITIS search (accessed 06/23/2019)
https://plants.usda.gov/java/nameSearch