Kallstroemia grandiflora
Arizona caltrop
(c) Alex Abair, some rights reserved (CC BY), uploaded by Alex Abair · licence
Family: Zygophyllaceae · Type: Herb · Not Native
Kallstroemia grandiflora (Arizona caltrop) is a non-native California herb in the Zygophyllaceae family, recognized by . Distinctive large petals (15-30mm) and elevation range.
Arizona caltrop is a naturalized annual found in southern desert regions near Desert Center and Jacumba in sandy roadsides at elevations of 300 to 900 meters. Flowering from September to October, this plant produces large yellow to orange flowers with darker bases, measuring 15 to 30 millimeters across. Growing with decumbent to ascending stems less than one meter tall, it is densely covered in silky hairs and sharp bristles. Its leaves feature 8 to 16 leaflets with small stipules 4 to 10 millimeters long. The fruit is a small ovoid structure 2 to 3 millimeters wide, with a style three times the length of the fruit body.
Identification and appearance
Key characters: Geographically isolated. Distinctive large petals (15-30mm) and elevation range
Habitat and range
Habitat: Uncommon. Sandy roadsides
Elevation: 300-900 m
California counties: Riverside, San Bernardino
Outside California: native Arizona to Texas, western Mexico
Bloom period
Kallstroemia grandiflora blooms Sep-Oct.
How to tell it apart
vs Tribulus: Kallstroemia fruits are bumpy but harmless; Tribulus fruits have 2-4 stout tire-puncturing spines.; vs Eschscholzia: Kallstroemia has compound feather-like leaves; Eschscholzia has finely dissected lacy leaves and bright orange poppy flowers.; vs Zygophyllum: Kallstroemia has 6-18 thin leaflets per leaf; Zygophyllum has only 2 thick fleshy leaflets.; vs Larrea: Kallstroemia is a sprawling annual with orange flowers; Larrea is an upright shrub with yellow flowers.; vs Fagonia: Kallstroemia has soft feather-like leaves without spines; Fagonia has three rigid spine-tipped leaflets per leaf.
Frequently asked questions
Is Kallstroemia grandiflora native to California?
No. Kallstroemia grandiflora is not native to California (recorded as not native).
When does Kallstroemia grandiflora bloom?
Kallstroemia grandiflora blooms Sep-Oct.
Where in California does Kallstroemia grandiflora grow?
Kallstroemia grandiflora occurs in Riverside, San Bernardino, at elevations of 300-900 m.
What plant family does Kallstroemia grandiflora belong to?
Kallstroemia grandiflora is in the Zygophyllaceae family, genus Kallstroemia.
What habitat does Kallstroemia grandiflora grow in?
Kallstroemia grandiflora grows in Uncommon. Sandy roadsides.
Related species
Other California species in the same genus, family, or bioregion.
Sources: Jepson eFlora · Index of California Plant Names · CalPhotos
Last updated 2026-10-07
Data from The California Species Project — 14,000+ California species with verified data from CNPS, CDFW, USFWS, Cal-IPC, and more.