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Identity of an Astragalus species near Terlingua, TX


Topic:
Author: Nan Hampton
Date: Tuesday - May 14, 2013
From: Terlingua, TX

QUESTION: I have been photographing as many of the wildflowers that I can this Spring 2013 season here in the Big Bend Area between BBNP, Terlingua and Alpine, TX. Two days ago I took a drive from Terlingua to Alpine and needless to say there was so many wildflowers that I did not have the time to take shots of them all. Most of them can be ID'd. However, I found one I've never seen before. I've narrowed it down to Astragalus but the actual species is a question mark. It appears as the same as the photo in your database, Astragalus thurberi. And again, however, your database says that the natural area is AZ and NM. I found the specimen on the stretch of Hwy 118 between what we locals refer to as "Trashcan Hill" (a knoll of Hwy 118 with pull off and a trashcan on each side) and the juncture of Hwy 118 and Terlingua Ranch Main Road. Along side of the Astragalus thurberi were the Tansy Aster/Desert Aster(?), Nodding Thistle, and Gyp Indian Blanket. All within a few feet of one another.

ANSWER:

Astragalus thurberi (Thurber's milkvetch) distribution, according to the USDA Plants Database, is a long way from Brewster County, Texas so I doubt that this is the identity of your plant.  You can see in the New Mexico county distribution map from the USDA Plants Database that it occurs in the southwest corner of New Mexico.

Below are the species of Astragalus that have been reported for Brewster County by the USDA Plants Database:

Astragalus allochrous (halfmoon milkvetch) and Astragalus allochrous var. playanus (halfmoon milkvetch)   Here are more photos and more information from Southwest Environmental Information Network.

Astragalus crassicarpus (Groundplum milkvetch)  Here are more photos and information from Plants for a Future.

Astragalus crassicarpus var. crassicarpus (Groundplum milkvetch)  Here are photos and information from Robert W. Freckmann Herbarium at the University of Wisconsin.

Astragalus emoryanus (Emory's milkvetch)

Astragalus emoryanus var. terlinguensis (Emory's milkvetch)

Astragalus humistratus (Groundcover milkvetch) and Astragalus humistratus var. humistratus (Groundcover milkvetch)

Here are photos and more information from Southwest Environmental Information Network, Vascular Plants of the Gila Wilderness and from CalPhotos.

Astragalus lotiflorus (Lotus milkvetch)  Here are more photos and information from Kansas Wildflowers & Grasses.

Astragalus missouriensis (Missouri milkvetch)  Here are more photos and information from USGS Northern Prairie Wildlife Research Center.

Astragalus missouriensis var. missouriensis (Missouri milkvetch)

Astragalus mollissimus (Purple locoweed)  Here are more photos and information from Southwest Colorado Wildflowers

Astragalus molissimus var. earlei (Purple locoweed)

Astragalus nuttallianus (Nuttall's milkvetch)  Here are more photos and information from Southwest Colorado Flowers.

Astragalus nuttallianus var. austrinus (Nuttall's milkvetch)

Astragalus wrightii (Wright's milkvetch)  Sorry, but there were no photos of this species on the internet that I could find.  Consulting Correll & Johnston "Manual of the Vascular Plants of Texas" I found this information: "petals reddish-violet, lilac, or whitish faintly lilac-tinged."

The different species of Astragalus are difficult to tell apart and the seed pod is often the determining factor instead of the flowers.  You really need the plant in hand and a good key such as Correll & Johnston (see above) to do this.

Best of luck with your quest and your photographs of the areas wildflowers.

From the Image Gallery


Astragalus thurberi

Astragalus crassicarpus

Astragalus crassicarpus

Astragalus crassicarpus var. crassicarpus

Astragalus emoryanus

Astragalus lotiflorus

Astragalus missouriensis

Astragalus mollissimus

Astragalus nuttallianus
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