CPC Plant Profile: Weber's Whitlow-grass
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Plant Profile

Weber's Whitlow-grass (Draba weberi)

  • Global Rank: G1 - Critically Imperiled
  • Legal Status: N/A
  • Family: Brassicaceae
  • State: CO
  • Nature Serve ID: 150672
  • Date Inducted in National Collection:

A perennial herb with erect stems about 2-10 cm long, and with yellow flowers in bloom in June and July. Draba weberi may differ from other species in its wetter habitat of stream edges, but the possibility that it can survive in less mesic areas cannot be ruled out.

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  • 09/09/2020
  • Orthodox Seed Banking

Seed collection and storage

  • 09/09/2020
  • Seed Collection

Seed collection and storage

Nature Serve Biotics
  • 05/02/2017

An extremely restricted Colorado endemic, known only from four populations totaling perhaps 300 individuals. Threats include hydrologic alterations, trampling by recreationist's, road and dam construction and maintenance, mining, spread of exotic species, and global climate change.

Price & Rollins, Mary VB Goshorn
  • 01/01/2010

Road and dam construction and maintenance are considered to be the primary threat to the species at this time (Rondeau et al. 2011). At the type locality, the population depends on water flowing from an outflow pipe below a dam that enters a relatively na

Price & Rollins, Mary VB Goshorn
  • 01/01/2010

There are 2 documented occurrences (EO data in the NatureServe central database as of July 2011; J. Handwerk, pers. comm., 2011).

Price & Rollins, Mary VB Goshorn
  • 01/01/2010


Price & Rollins, Mary VB Goshorn
  • 01/01/2010

No management plans or conservation strategies have been developed for D. weberi, and the single known location does not have any protective designation.

Price & Rollins, Mary VB Goshorn
  • 01/01/2010

The most pressing need is to locate additional populations of Draba weberi, if any exist. If additional populations of D. weberi are located, especially on National Forest System land, our knowledge of conditions appropriate for conserving the species will be enhanced. Until additional occurrences are located, monitoring of the single known population is also very important. Given the small number of known individuals, there is insufficient material to allow manipulative investigations of Draba weberis life cycle, habitat relations, population trends, and response to disturbance. Likewise, metapopulation dynamics are irrelevant if this is the only population. However, these topics are essentially completely unexplored, and observations that would add to our knowledge on any of these subjects would be helpful in determining the effects of land management practices on the survival and persistence of the species and in formulating management and conservation plans.

Price & Rollins, Mary VB Goshorn
  • 01/01/2010

Seed collection and storage


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Taxon Draba weberi
Authority R.A. Price & Rollins
Family Brassicaceae
CPC Number 44486
ITIS 506951
Common Names Weber's Whitlow grass | Weber whitlowgrass | Weber's draba
Associated Scientific Names Draba weberi
Distribution Known from the type locality in Summit County, Colorado and recently discovered at one site in Park County, Colorado (J. Handwerk, pers. comm., 2011).
State Rank
State State Rank
Colorado S1

Amid rocks along streamlets near timberline (about 3500 m elevation) (Flora of North America Editorial Committee 2010).The streamside habitat of Draba weberi is wetter than that reported for nearby related Draba species. Plants occupy crevices among streamside rocks below the dam. This species was not collected before the construction of the dam, so it is impossible to know whether its current habitat is equivalent to its pre-dam environment, or indeed representative of its optimal habitat. Reported population numbers are small, and there is additional unoccupied suitable habitat along the drainage for about 1/2 mile below the dam, as well as potentially similar habitat available in nearby drainages of the Tenmile Range (Olson personal communication 2004).

Ecological Relationships

Draba weberi shares the trait of other Colorado endemic species of having sterile pollen and anthers that do not dehisce. These species appear to reproduce asexually through agamospermy, which is a form of apomixis in which seeds are formed without fertilization and carry only maternal genes. This form of reproduction has also been reported for several other yellow-flowered, arctic-alpine Draba species in North America (Mulligan and Findlay 1970, Mulligan 1976). Rollins (1993) speculated that the failure to produce viable pollen may have evolved in connection with the breakdown of the sexual system of reproduction in harsh arctic or alpine environments. Asexual reproduction may allow D. weberi to achieve a higher reproductive potential than high-elevation species that must rely on pollinators.Environmental specificity very narrow. Specialist or community with key requirements scarce.

Common Name Name in Text Association Type Source InteractionID
Lead Institution State Reintroduction Type Year of First Outplanting

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