Thelesperma megapotamicum
Rayless greenthread, Rayless Greenthread
(c) Reid Hardin, some rights reserved (CC BY) · licence
Family: Asteraceae · Type: Herb · Not Native
Thelesperma megapotamicum (Rayless greenthread) is a non-native California herb in the Asteraceae family, recognized by Only Thelesperma species established in California, waif from South American range.
Rayless greenthread is a naturalized perennial found in southern California, including Santa Catalina Island and the Peninsular Ranges, on disturbed ground at elevations below 500 meters. Flowering from May to October, this plant produces yellow to orange disk flowers without ray flowers in heads 5 to 8 millimeters wide. Growing with few-branched glaucous stems 30 to 80 centimeters tall that are smooth and bluish-green, it has a distinctive branching habit. Its leaves are 3 to 12 centimeters long, with lower leaves finely divided into linear segments in a 1 to 2-pinnate pattern. The fruit is dark, 4 to 8 millimeters long, with short stout pappus awns 1 to 2 millimeters in length.
Identification and appearance
Key characters: Only Thelesperma species established in California, waif from South American range
Habitat and range
Habitat: Disturbed ground
Elevation: < 500 m
Outside California: native Wyoming to Arizona, Texas, northern Mexico, also South America
Bloom period
Thelesperma megapotamicum blooms (Apr)May-Oct.
How to tell it apart
vs Eriophyllum: Thelesperma has thread-thin leaf segments; Eriophyllum has woolly, broader lobed leaves.; vs Encelia: Thelesperma has thread-like divided leaves; Encelia has broad, undivided triangular or ovate leaves.; vs Helichrysum: Thelesperma has thread-thin green leaves; Helichrysum has rounded silvery-woolly leaves.; vs Bebbia: Thelesperma has thread-like leaf divisions; Bebbia has simple linear leaves that are rough but not divided.; vs Crupina: Thelesperma has thread-like leaf segments throughout; Crupina has broader lower leaves and only upper leaves finely divided.
Frequently asked questions
Is Thelesperma megapotamicum native to California?
No. Thelesperma megapotamicum is not native to California (recorded as not native).
When does Thelesperma megapotamicum bloom?
Thelesperma megapotamicum blooms (Apr)May-Oct.
What plant family does Thelesperma megapotamicum belong to?
Thelesperma megapotamicum is in the Asteraceae family, genus Thelesperma.
What habitat does Thelesperma megapotamicum grow in?
Thelesperma megapotamicum grows in Disturbed ground.
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.