CPC Plant Profile: Prairie Dawn
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Plant Profile

Prairie Dawn (Hymenoxys texana)

The yellow flowers of Hymenoxys texana are usually found from late March to early April (shown here in an greenhouse at the Mercer Arboretum). Photo Credit: Stephen M. Young
Description
  • Global Rank: G2 - Imperiled
  • Legal Status: Federally Endangered
  • Family: Asteraceae
  • State: TX

Prairie dawn is a member of the sunflower family, but this small annual only reaches a height of seven inches and so is often overlooked. This plant is found only in the open grasslands of the northern part of the Gulf Prairie region of Harris and Fort Bend Counties of Texas. In late winter its oblong, somewhat fleshy leaves cluster at the plant base and in late February to April a small (0.15-0.23 inch long) round head of yellow disk flowers appears. The minute ray flowers are concealed by the bracts. The plant sets seeds from April to May and dies before the bare ground dries and cracks in the summer heat. The seeds are cone-shaped and hairy. (Stark 1996). Prairie Dawn was first collected near Hockley in Harris County, Texas in 1889. Thought to be extinct (Correll and Johnston 1979), the plant was rediscovered north of Cypress in Harris County in 1981 by James Kessler (Mahler 1982 & 1983).

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Nomenclature
Taxon Hymenoxys texana
Authority (Coult. & Rose) Cockerell
Family Asteraceae
CPC Number 2296
ITIS 37788
USDA HYTE5
Common Names prairie dawn | Texas bitterweed | Texas prairie dawn-flower
Associated Scientific Names Hymenoxys texana
Distribution Endemic to the Gulf Coastal Prairie of Harris, Fort Bend and Trinity Counties, Texas.
State Rank
State State Rank
Texas S2
Habitat

Grows within a narrow range of soil and site conditions in the open grasslands of the northern part of the Gulf Prairie region. Slick areas composed of fine-sandy compacted soil occur in seasonally wet depressions or saline swales at the periphery of low mounds termed mima or pimple mounds (Stark 1996). The upper 7 inches of the soils, in the Narta soil series, are poorly drained and are powdery when dry and sticky and soft when wet. These soils are often saline and moderately alkaline. Little water is available to plant roots beyond the upper 7 inches. Plants endure soil conditions ranging from saturated during the winter to droughty in the summer. Hymenoxys texana also persists in the low areas of abandoned rice fields, vacant lots, and pastures where mima mounds have been bulldozed and natural vegetation has returned. Prairie Dawn does not colonize recently disturbed soils and is susceptible to competition.Plants that grow in association with Prairie Dawn include Short-spike Windmillgrass, the rare Texas Windmillgrass, Gulf Cordgrass, Whorled Dropseed, Filly Panicum, Little Barley, Annual Bentgrass, Bearded Flatsedge, False Onion, Bottlebrush Plantain, Pepperweed, Sandparsley, the rare Houston Camphor Daisy, Western Dwarf-dandelion, Chaffweed, Golden Hedgehyssop, Common evax, Prairie Flameflower, Purslane, Wine-cup, Cotton-flower, Silky Evolvulus and Bracted Sida (Stark 1996).

Ecological Relationships

Changes in soil salinity and acidity occur in these areas as result of the fluctuating water table. Blue-green alga, Nostoc, often covers the barren or sparsely vegetated microhabitats where Prairie Dawn is found. Prairie Dawn and other annuals that persist in these conditions complete their life cycles during the favorable conditions in early Spring. (Stark 1996).

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Pollinators
Common Name Name in Text Association Type Source
Other
Thrips Microcephalothips abdominalis Suspected Pollinator Floral Link

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