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     Intermountain Flora combines all local members of the Thermopsis genus into one species, T. rhombifolia, with a number of varieties, including Thermopsis rhombifolia variety montana. Weber and the Synthesis of the North American Flora recognize T. montana, T. divaricarpa, and T. rhombifolia as distinct species. Welsh recognizes both T. rhombifolia and T. montana in Utah, noting, however, that Utah specimens of the latter "demonstrate a wide range of variation..., [but] there appears to be no basis for segregation of subordinate taxa". Welsh also notes that in Utah T. rhombifolia is at the "margin of its range".

    T. rhombifolia is primarily a species of the northern Rockies, found also in a few southern counties of Colorado with a relatively disjunct population in a few northwestern counties of New Mexico. It is not found in Arizona and occurs in Utah in just two counties in the very northeast corner. The New Mexico species shown below is far from the main northern populations of T. rhombifolia and might very well be a new species or variety.

     Click for Thermopsis montana.

Thermopsis rhombifolia (Golden Banner)
Fabaceae (Pea Family)

Semi-desert, foothills. Woodlands, meadows, openings. Spring.
De-Na-Zin/Bisti Wilderness, New Mexico, April 18, 2005.

Leaves of Thermopsis rhombifolia are usually shorter and broader than those of Thermopsis montana and seed pods are strongly curved. T. rhombifolia grows 6-18 inches tall; T. montana grows over several feet tall. But even more important in distinguishing Thermopsis rhombifolia from Thermopsis montana is the habitat: T. rhombifolia is a dweller of lower altitudes, prairies, and sandy, dry areas. T. montana grows in more moist meadows and woodlands of the lower mountains. In the De-Na-Zin/Bisti Wilderness area, T. rhombifolia grows on hot, dry, sandy/gravelly hillsides in large patches. It blooms early but its erect, dried stems and its leaves are still evident the following year.

In 1814 Thomas Nuttall named this plant Cytisus rhombifolius from a specimen collected by Bradbury. Nuttall renamed the plant Thermia rhombifolia in his Genera of North American Plants in 1818 (click the title to read), and Richardson named it Thermopsis rhombifolia in 1823.

Thermopsis rhombifolia (Golden Banner)
Fabaceae (Pea Family)

Semi-desert, foothills. Woodlands, meadows, openings. Spring.
De-Na-Zin/Bisti Wilderness, New Mexico, April 18, 2005.

Thermopsis rhombifolia
Thermopsis rhombifolia (Golden Banner)
Fabaceae (Pea Family)
 

Semi-desert, foothills. Woodlands, meadows, openings. Spring.
De-Na-Zin/Bisti Wilderness, New Mexico, May 21, 2009.

For several years Betty and I (and pup Willi) visited De-Na-Zin to collect seed pods so we could be positive of the identification of this species. Either we were too early, too late, or small critters had eaten all the seeds. In 2009 we were at De-Na-Zin at the right time but we found that almost no plants had flowered and the few that had, retained almost none of their seed pods. We did manage to find about a dozen seed pods.  Those pictured at left are about 3 centimeters long and are not mature. Compare them with the seed pods of Thermopsis montana.

Thermopsis rhombifolia (Golden Banner)
Fabaceae (Pea Family)

Semi-desert, foothills. Woodlands, meadows, openings. Spring.
De-Na-Zin Wilderness/Bisti, New Mexico, April 18, 2005.

Thermopsis rhombifolia spreads in large colonies from root sprouts. In the photo at left, and even more noticeably in the photo below, one can see that these plants often grow in straight lines; the roots are finding and following underground seeps.

Thermopsis rhombifolia (Golden Banner)
Fabaceae (Pea Family)

Semi-desert, foothills. Woodlands, meadows, openings. Spring.
De-Na-Zin Wilderness/Bisti, New Mexico, April 23, 2007.

Click for Thermopsis montana.

Thermopsis rhombifolia (Golden Banner)
Fabaceae (Pea Family)

Semi-desert, foothills. Woodlands, meadows, openings. Spring.
De-Na-Zin Wilderness/Bisti, New Mexico, April 23, 2007.

Some critter loves to eat Thermopsis rhombifolia flower stems, leaving the flowers to carpet the path to their den. The den hole in the rocks is just big enough to put your hand into.

Thermopsis rhombifolia (Golden Banner)
Fabaceae (Pea Family)

Semi-desert, foothills. Woodlands, meadows, openings. Spring.
De-Na-Zin Wilderness/Bisti, New Mexico, April 23, 2007.

A group of plant lovers examines T. rhombifolia.

Thermopsis rhombifolia (Golden Banner)
Fabaceae (Pea Family)

Semi-desert, foothills. Woodlands, meadows, openings. Spring.
De-Na-Zin Wilderness/Bisti, New Mexico, April 23, 2007.

As the Society members examined this species of Thermopsis we realized that it possessed some traits that seemed to set it off from other T. rhombifolia and we thought it best to study the plant in more detail when we had access to a microscope and a number of botanical texts. Loraine Yeatts is shown preparing a specimen to dry.

Range map © John Kartesz,
Floristic Synthesis of North America

State Color Key

Species present in state and native
Species present in state and exotic
Species not present in state

County Color Key

Species present and not rare
Species present and rare
Species extirpated (historic)
Species extinct
Species noxious
Species exotic and present
Native species, but adventive in state
Eradicated
Questionable presence

Range map for Thermopsis rhombifolia