Thermopsis rhombifolia

Thermopsis rhombifolia or T. r. divaricarpa or T. r. montana
 or varieties as full species Golden Pea or Mountain Golden Pea
 Hillsboro Peak Trail, Black Range
May 25, 2015

One of the more common flowers that you are likely to encounter on a walk along the Hillsboro Peak Trail in May is a Thermopsis sp.. If you are a lumper and follow Intermountain Flora, then this is the Golden Pea, Thermopsis rhombifolia.  There are two varieties of T. rhombifolia which are likely to be found in the Black Range, T. r. divaricarpa (Golden Pea) and T. r. montana (Mountain Golden Pea).  They are typically found in association with Ponderosa Pine forest and bloom in the early spring (but note the effect of elevation on bloom time).  This species is found in most of the southern provinces of Canada and most of the central United States, where it bears the common names of Prairie Thermopsis and Prairie Goldenbean.

If you are a splitter and follow The Biota of North America Program - North American Vascular Flora (BONAP) then the two varieties mentioned above are considered full species; T. divaricarpa is known as Golden Pea and T. montana is known as Mountain Golden Banner.  

BONAP shows the range of T. montana to the right.  The light green color indicates that the species is present in a county and is not rare.  The dark green color indicates that the species is present in the state.  BONAP shows range maps for T. rhombifolia and T. divaricarpa with light green only in the northern counties of New Mexico.  My understanding of their protocol is that a county shown in dark green may be populated by a species but that it is not common.  Vascular Plants of the Gila Wilderness, includes both T. divaricarpa and T. montana (as varieties of T. rhombifolia).  

I am not qualified to speak to this question of speciation and leave it to you to decide.  Apparently, however, the habit of the seed pods can be used to distinguish between the two species (or varieties).  The seed pods of T. montana are erect, covered with downy hair and form vertically from the stem, while the pods of T. divaricarpa form laterally. 

This species was used by the native peoples as a yellow dye and as atea used to address stomach problems.  Interestingly, it is toxic and symptoms following ingestion include dizziness, vomiting, and abdominal pain.

Sawyers Peak Trail, Black Range
May 13, 2021
Photograph immediately above and two immediately below


Railroad Canyon, Black Range, NM
May 9, 2014

Sawyer’s Peak Trail, Black Range - May 31, 2019

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