Diodia teres
Rough buttonweed, poor joe, Poor Joe
(c) Sandy Wolkenberg, some rights reserved (CC BY) · licence
Family: Rubiaceae · Type: Herb · Native
Diodia teres (Rough buttonweed) is a native California herb in the Rubiaceae family, recognized by Eastern North American species reaching its western limit as a waif in California's Sonoran Desert.
Rough buttonweed is a naturalized annual found in the southeastern Imperial County desert regions on dry mesas and sandy slopes at an elevation of 50 meters. Flowering from June to October, this plant produces small white or pink flowers approximately 3 millimeters long. Growing with erect stems 7 to 25 centimeters tall that are 4-angled and sometimes branched, it has a distinctive growth habit. Its leaves are lanceolate, reaching 2.5 centimeters long, with transparent stipules at the base forming a cup-like structure that partially encloses the flower cluster. The plant has stiff, unequal calyx lobes that contribute to its characteristically rough appearance.
Identification and appearance
Key characters: Eastern North American species reaching its western limit as a waif in California's Sonoran Desert
Habitat and range
Habitat: dry mesas, slopes, often sandy
Elevation: 50 m
California counties: Imperial
Outside California: to eastern United States, Mexico
Bloom period
Diodia teres blooms Jun-Oct.
How to tell it apart
vs Kelloggia: Diodia has stalkless flowers at leaf joints; Kelloggia has long-stalked flowers in open terminal clusters.; vs Crucianella: Diodia has opposite leaves and flowers at nodes; Crucianella has whorled leaves and dense terminal spikes.; vs Sherardia: Diodia has opposite leaves and desert habitat; Sherardia has whorled leaves and disturbed non-desert sites.; vs Galium: Diodia has opposite leaves and stalkless flowers; Galium has whorled leaves and stalked flowers in clusters.; vs Coprosma: Diodia is herbaceous with tiny flowers at nodes; Coprosma is a woody shrub with separate male-female plants.
Frequently asked questions
Is Diodia teres native to California?
Yes. Diodia teres is native to California (recorded as native).
When does Diodia teres bloom?
Diodia teres blooms Jun-Oct.
Where in California does Diodia teres grow?
Diodia teres occurs in Imperial, at elevations of 50 m.
What plant family does Diodia teres belong to?
Diodia teres is in the Rubiaceae family, genus Diodia.
What habitat does Diodia teres grow in?
Diodia teres grows in dry mesas, slopes, often sandy.
Related species
Other California species in the same genus, family, or bioregion.
Sources: Jepson eFlora · 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.