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Plant Profile

Prairie Dawn (Hymenoxys texana)

Plants of Hymenoxys texana blooming at the Harris County Prairie Dawn Preserve with Opuntia humifusa, Eastern prickly pear cactus on March 24, 2021.

Photo Credit: Mercer Botanic Gardens
  • Global Rank: G2 - Imperiled
  • Legal Status: Federally Endangered
  • Family: Asteraceae
  • State: TX
  • Nature Serve ID: 153540
  • Lifeform: Forb/herb
  • Date Inducted in National Collection: 03/05/1993
Description:

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).

Where is Prairie Dawn (Hymenoxys texana) located in the wild?

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).

Distribution:

Endemic to the Gulf Coastal Prairie of Harris, Fort Bend and Trinity Counties, Texas.

States & Provinces:

Prairie Dawn can be found in Texas

Which CPC Partners conserve Prairie Dawn (Hymenoxys texana)?

CPC's Plant Sponsorship Program provides long term stewardship of rare plants in our National Collection. We are so grateful for all our donors who have made the Plant Sponsorship Program so successful. We are in the process of acknowledging all our wonderful plant sponsorship donors on our website. This is a work in progress and will be updated regularly.

Conservation Actions

Tina Stanley
  • 05/27/2024
  • Orthodox Seed Banking

Samples of seeds collected by Mercer Botanic Gardens from H. texana from the Harris County Prairie Dawn Preserve site are used for researching the aging and longevity of the seeds of this species. The seed research is conducted at the National Laboratory for Genetic Resource Preservation (NLGRP) with funding from a Museum of Library Services National Leadership Grant (MG-245983-OMS-20).

Tina Stanley
  • 05/27/2024
  • Seed Collection Orthodox Seed Banking

Mercer Botanic Gardens manages the Harris County Prairie Dawn Preserve for naturally occurring populations of the endangered annual prairie wildflower, Hymenoxys texana, Texas prairie dawn and three rare saline prairie associates,  Rayjacksonia aurea, Houston camphor daisy; Chloris texensis, Texas windmill grass; and Liatris bracteata, coastal gayfeather. Long-term studies that began in 2013 at the preserve will provide important information about the abiotic and biotic requirements of H. texana and its rare associate species. Samples of seeds collected from H. texana from the preserve site are used for researching the aging and longevity of the seeds of this species. The seed research is conducted at the National Laboratory for Genetic Resource Preservation (NLGRP) with funding from a Museum of Library Services National Leadership Grant (MG-245983-OMS-20).

Center for Plant Conservation
  • 08/18/2021
  • Orthodox Seed Banking

In 2021, CPC contracted the Mercer Botanic Gardens to recollect seed from a population currently held in long term orthodox seed storage as part of an IMLS-funded seed longevity experiment. The National Laboratory for Genetic Resources Preservation will evaluate how germination tested viability and RNA Integrity of seed lots decline over time in storage.

  • 10/17/2020
  • Orthodox Seed Banking

Mercer also banks subsets of rare seeds collected from field surveys and from propagation work with our collaborating CPC institution, the Lady Bird Johnson Wildflower Center, Austin, TX and the National Center for Genetic Resources Preservation (NCGRP) in Ft. Collins, CO (formerly called the National Seed Storage Laboratories. Seeds from an in-house propagation of 1993 that had been in storage in Mercer's seed bank freezer germinated under greenhouse conditions at ~70% with ~50% survivorship during the Winter of 2001.

  • 10/17/2020
  • Seed Collection

Seeds from several sites within Harris County collected by Dr. Larry Brown of Houston Community College and Ralph Taylor of the Harris County Flood Control District are stored at Mercer Arboretum and Botanic Gardens. Banked wild-collected seed date to 1988. Mercer also banks subsets of rare seeds collected from field surveys and from propagation work with our collaborating CPC institution, the Lady Bird Johnson Wildflower Center, Austin, TX and the National Center for Genetic Resources Preservation (NCGRP) in Ft. Collins, CO (formerly called the National Seed Storage Laboratories. Seeds from an in-house propagation of 1993 that had been in storage in Mercer's seed bank freezer germinated under greenhouse conditions at ~70% with ~50% survivorship during the Winter of 2001.

  • 10/17/2020
  • Living Collection

The Endangered Species Garden established in 1994 with support from Star Enterprises displays rare native plants for the public to view year-round. Plants germinated in our greenhouses are used for display in our Endangered Species Garden and Mercer's Plaza and displays for off-site conservation programs given by Mercer.

  • 10/17/2020
  • Propagation Research

Germination and growth to maturity studies at Mercer Arboretum and Botanic Gardens in 1988-89 revealed non-specific soil requirements and ease of cultivation. Seedlings, however, do not tolerate extended periods of submerging. Public educational display plants for the Endangered Species Garden at Mercer are germinated within our greenhouses.In Spring 2002, the River Oaks Garden Club of Houston, TX provided a generous gift to begin the expansion and renovation of Mercers Endangered Species Garden. Plants produced for educational display gardens or for specific restoration and reintroduction projects are produced within Mercers nursery greenhouses and within our Conservation Area. The Conservation Area provides secure, raised beds for mass propagation of plants/seeds. Each bed is provided with independently controlled irrigation and substrates that meet the unique requirements for each species. Seeds from several sites within Harris County collected by Dr. Larry Brown of Houston Community College and Ralph Taylor of the Harris County Flood Control District are stored at Mercer Arboretum and Botanic Gardens. Banked wild-collected seed date to 1988. Mercer also banks subsets of rare seeds collected from field surveys and from propagation work with our collaborating CPC institution, the Lady Bird Johnson Wildflower Center, Austin, TX and the National Center for Genetic Resources Preservation (NCGRP) in Ft. Collins, CO (formerly called the National Seed Storage Laboratories. Seeds from an in-house propagation of 1993 that had been in storage in Mercer's seed bank freezer germinated under greenhouse conditions at ~70% with ~50% survivorship during the Winter of 2001. Plants germinated in our greenhouses are used for display in our Endangered Species Garden and Mercer's Plaza and displays for off-site conservation programs given by Mercer. http://www.cp4.hctx.net/mercer/mplant.htm. This article appeared in Harris County Precinct 4 magazine, Parkscape, Autumn 2001 and reached 33,000 possible readers. Harris County Precinct 4 magazine, Parkscape publishes public information articles about the plant conservation efforts of Mercer Arboretum and Botanic Gardens. 115,000 issues are circulated annually of this quarterly publication. Articles about rare plants maintained at Mercer may be viewed at: http://www.cp4.hctx.net/mercer/mplant.htm.

  • 10/17/2020
  • Genetic Research

Genetic studies completed by L. Brown and J.L. Strother (1988) documented disploidy, 2N= 16 and 6 in Hymenoxys texana.

Elvia Ryan
  • 08/13/2018

Mercer Botanic Gardens maintains the Harris County Precinct 4 Prairie Dawn Preserve.  This is four acre preserve which shelters four naturally-occurring rare prairie species which includes Hymenoxys texana.  The floods of April and May of 2016 and Hurricane Harvey of 2017 have affected the drainage patterns causing erosion issues on this preserve.  Surveys conducted in April 2018 show that ~1000 more Hymenoxys texana (Texas prairie dawn plants) than the ~60 counted before Hurricane Harvey struck in 2017.  More than 10,000 were counted in 2016 before the floods of April and May 2016.  It is the belief of the Mercer Botanic Gardens that Hymenoxys texana is rebounding.  (Tiller et al. 2018)

Nature Serve Biotics
  • 05/02/2017

Endemic to?saline prairies with cryptogamic soils within the Houston Coastal Prairie. Although nearly 60 sites are known for this species, almost all are threatened by development from the expanding city of Houston. Many of the sites are within 1 km of each other and probably form a single population. Some sites have been destroyed within a year of their discovery due to development.

Dave Berkshire
  • 01/01/2010

Competition from woody vegetation heavy grazing by cattle and primarily, urban development (road construction and residential development) of the Coastal Prairies, especially within the Houston city limits where these plants are found.

Dave Berkshire
  • 01/01/2010

Since 1986, populations found in Harris and Fort Bend Counties may total ~ 50 sites comprising an unknown number of individuals (Stark 1996).

Dave Berkshire
  • 01/01/2010

Genetic studies completed by L. Brown and J.L. Strother (1988) documented disploidy, 2N= 16 and 6 in Hymenoxys texana. Germination and growth to maturity studies at Mercer Arboretum and Botanic Gardens in 1988-89 revealed non-specific soil requirements and ease of cultivation. Seedlings, however, do not tolerate extended periods of submerging. Public educational display plants for the Endangered Species Garden at Mercer are germinated within our greenhouses. The Endangered Species Garden established in 1994 with support from Star Enterprises displays rare native plants for the public to view year-round. In Spring 2002, the River Oaks Garden Club of Houston, TX provided a generous gift to begin the expansion and renovation of Mercers Endangered Species Garden. Plants produced for educational display gardens or for specific restoration and reintroduction projects are produced within Mercers nursery greenhouses and within our Conservation Area. The Conservation Area provides secure, raised beds for mass propagation of plants/seeds. Each bed is provided with independently controlled irrigation and substrates that meet the unique requirements for each species. Seeds from several sites within Harris County collected by Dr. Larry Brown of Houston Community College and Ralph Taylor of the Harris County Flood Control District are stored at Mercer Arboretum and Botanic Gardens. Banked wild-collected seed date to 1988. Mercer also banks subsets of rare seeds collected from field surveys and from propagation work with our collaborating CPC institution, the Lady Bird Johnson Wildflower Center, Austin, TX and the National Center for Genetic Resources Preservation (NCGRP) in Ft. Collins, CO (formerly called the National Seed Storage Laboratories. Seeds from an in-house propagation of 1993 that had been in storage in Mercer's seed bank freezer germinated under greenhouse conditions at ~70% with ~50% survivorship during the Winter of 2001. Plants germinated in our greenhouses are used for display in our Endangered Species Garden and Mercer's Plaza and displays for off-site conservation programs given by Mercer. http://www.cp4.hctx.net/mercer/mplant.htm. This article appeared in Harris County Precinct 4 magazine, Parkscape, Autumn 2001 and reached 33,000 possible readers. Harris County Precinct 4 magazine, Parkscape publishes public information articles about the plant conservation efforts of Mercer Arboretum and Botanic Gardens. 115,000 issues are circulated annually of this quarterly publication. Articles about rare plants maintained at Mercer may be viewed at: http://www.cp4.hctx.net/mercer/mplant.htm.

Dave Berkshire
  • 01/01/2010

Semi-protected on 2 sites with a good possibility for management. Current management includes monitoring and seasonal mowing/burning of sites where possible.

Dave Berkshire
  • 01/01/2010

Further develop protected sanctuaries within Harris and Ft. Bend Counties.

Dave Berkshire
  • 01/01/2010

Expand seed bank. Propagation of seed for reintroduction efforts.

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Nomenclature
Taxon Hymenoxys texana
Authority (Coult. & Rose) Cockerell
Family Asteraceae
CPC Number 2296
ITIS 37788
USDA HYTE5
Duration Annual
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
Ecological Relationships

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

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