North America, Mexico, West Indies, Central America, South America, Eurasia, Africa, Atlantic Islands, Indian Ocean Islands, Pacific Islands, Australia, mostly tropical or subtropical regions, mainly in arid and semiarid areas.
Genera 27, species ca. 240 (6 genera, 15 species in the flora).
Zygophyllaceae are most closely related to Krameriaceae and the two families make up the isolated order Zygophyllales (Angiosperm Phylogeny Group 2003). A number grow in saline soils. Three species are cultivated in milder winter areas of the southeastern United States for their colorful flowers: the South American Bulnesia arborea (Jacquin) Engler and B. sarmientoi Lorentz ex Grisebach, both verawood, and the Caribbean Guaiacum officinale Linnaeus, lignum vitae. Guaiacum coulteri A. Gray, guayacán, from western Mexico and Guatemala, is grown in southern Arizona. Peganum, often placed in the Zygophyllaceae, is now recognized to be a member of the unrelated Nitrariaceae (Angiosperm Phylogeny Group).
|1||Leaflets 2.||> 2|
|2||Leaflets connate basally, leaves appearing simple and 2-lobed.||Larrea|
|1||Leaflets (1–)3 or (4–)6–16(–20).||> 3|
|3||Leaves palmately compound; leaflets (1–)3, apex spinose or spinulose.||Fagonia|
|3||Leaves pinnately compound; leaflets (4–)6–16(–20), apex not spinose.||> 4|
|4||Trees or shrubs; petals usually blue to purple, rarely white; fruits capsules, 2–5-lobed.||Guaiacum|
|4||Herbs; petals white or yellow to bright orange, bases sometimes green or red; fruits schizocarps, 5-angled or 10-lobed.||> 5|
|5||Ovaries 5-lobed, 5-locular; fruits 5-angled, spiny, breaking into 5 mericarps (rarely fewer); petals yellow, base darker; nectary 10 glands in 2 whorls.||Tribulus|
|5||Ovaries 10-lobed, 10-locular; fruits 10-lobed, not spiny, breaking into 10 mericarps (sometimes fewer); petals white to bright orange, base white to bright orange or green to red; nectary 5 glands at bases of filaments opposite petals.||Kallstroemia|