How to know the Texas Arabideae (Genera Draba, Abdra, and Tomostima)

Species of the Tribe Arabideae are among the first flowers to bloom (January--March or early April). Being small and inconspicuous, they are often overlooked (especially Draba reptans. Observations of Texas Arabideae are here. These species have been lumped and split, taxonomically; recently, all were in the genus Draba. The following characteristics vary, so documenting multiple characteristics will confirm the ID. Features to capture include:

• side view of mature fruits (pods)
• side view of flowering stem (pedicel) from top to bottom (with hairs in focus)
• view of leaves

Also, young plants may be challenging or impossible to identify.

• 1. The hairs on leaves and stems lie flat (appressed); mature fruit <5 mm long: Abdra brachycarpa (formerly Draba) [resource]
  


• 1. The hairs on leaves and stems are upright (perpendicular to surface); mature fruit 5-15 mm long




• 2. Pedicels (flowering stem) smooth (glabrous); leaves always entire (not notched): Tomostima reptans (formerly Draba) [resource]


• 2. Pedicels pubescent; at least some leaves usually with 1+ pair of teeth
  
  
  
  • 3. Leaves crowded near base; fruit elongate, blade-like; hairs along the stem branched: Draba cuneifolia [resource]
  
  
  • 3. Leaves extending up stem: fruit oval, football-shaped; many hairs along the stem unbranched: Draba platycarpa [resource]
  
  




*There is also a yellow-flowered species in Jeff Davis county (Trans-Pecos): Draba standleyi

Posted by pfau_tarleton, November 23, 2019 15:59