Hemizonia congesta subsp. congesta
Congested-headed hayfield tarplant, Congested-Headed Hayfield Tarplant
Photo: parent species Hemizonia congesta · (c) Bruce Homer-Smith, some rights reserved (CC BY) · licence
Family: Asteraceae · Type: Herb · Native
Conservation status: CNPS 1B.2
Hemizonia congesta subsp. congesta (Congested-headed hayfield tarplant) is a native California herb in the Asteraceae family, recognized by 5 sympatric subspecies. Key diagnostic: heads in tight groups, no calyx-like bracts, phyllary tips > bodies.
Congested-headed hayfield tarplant is a rare (CNPS 1B.2) California native annual found in southern North Coast Ranges, southwestern North Coast Ranges, northern Central Coast, and western San Francisco Bay Area in grassy sites and marsh edges at elevations below 100 meters. Flowering from May to November, this plant produces white ray flowers with distinct purple veining on the underside, arranged in tight, compact clusters. Growing with shaggy, glandular stems that have longer hairs along leaf margins, it reaches heights typical of slender annual herbs. Its leaves are characterized by variable hair coverage, with distal leaves often having longer marginal hairs and sparse glandular surfaces. The fruit is compact, with a width approximately half its length.
Identification and appearance
Key characters: 5 sympatric subspecies. Key diagnostic: heads in tight groups, no calyx-like bracts, phyllary tips > bodies
Habitat and range
Habitat: Grassy sites, marsh edges
Elevation: < 100 m
Bloom period
Hemizonia congesta subsp. congesta blooms May-Nov.
Conservation status
CNPS 1B.2
How to tell it apart
vs Deinandra: Hemizonia rays often purple-veined beneath; Deinandra rays pure yellow without veining.; vs Madia: Hemizonia has paleae throughout disk; Madia has ray fruits enclosed by phyllaries.; vs Calycadenia: Hemizonia rays shallowly lobed; Calycadenia rays deeply split into spreading lobes.; vs Holocarpha: Hemizonia lacks pit glands on stalks; Holocarpha has distinctive pit-gland-tipped stalk bracts.; vs Anisocarpus: Hemizonia has chaff throughout flower disk; Anisocarpus typically lacks chaff scales.
Frequently asked questions
Is Hemizonia congesta subsp. congesta native to California?
Yes. Hemizonia congesta subsp. congesta is native to California (recorded as native).
When does Hemizonia congesta subsp. congesta bloom?
Hemizonia congesta subsp. congesta blooms May-Nov.
What plant family does Hemizonia congesta subsp. congesta belong to?
Hemizonia congesta subsp. congesta is in the Asteraceae family, genus Hemizonia.
Is Hemizonia congesta subsp. congesta rare or endangered?
Hemizonia congesta subsp. congesta carries California Rare Plant Rank 1B.2, state rank S2.
What habitat does Hemizonia congesta subsp. congesta grow in?
Hemizonia congesta subsp. congesta grows in Grassy sites, marsh edges.
Related species
Other California species in the same genus, family, or bioregion.
Sources: Jepson eFlora · CNPS Rare Plant Inventory · Index of California Plant Names · CalPhotos · CDFW CNDDB
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.