Astragalus pattersonii [Patterson's Milkvetch]

[Andrea B.]

Blum, A.G. (2013) Astragalus pattersonii A. Gray ex Brandegee (Fabaceae) Patterson's Milkvetch. Flowers photographed in visible and ultraviolet light. http://www.ultraviol...sons-milkvetch/

Mesa Verde National Park, Montezuma County, Colorado, USA

02 May 2013

Wildflower

 

Comment:

There are many Astragalus in Colorado, and they are not always easy to sort out. Two key points in identifying this A. pattersonii are the reddish stems and the narrow, curved calyx lobes which appear almost fringed. In UV the inflorescence is complex. The calyx appears UV-dark but exhibits a great deal of iridescense. The flower is standardized false blue. So the overall impression of the flower stalk in UV is that it has a rather patchy appearence.

 

Reference:

1. Weber & Wittmann (2012) Astragalus L., page 191. Colorado Flora: Western Slope, 4th Ed. The U. of Colo. Press, Boulder, CO.

 

Equipment: [Nikon D600-broadband + Nikon 105mm f/4.5 UV-Nikkor]

 

Visible Light [f/8 for 1/1000" @ ISO 200 with Nikon Coolpix A]

 

Visible Light [f/8 for 1/2500” @ ISO 635 in Sunlight with Baader UVIR-Block Filter]

The mature flower is primarily white, but there is a lot of reflection happening in this particular shot which lends some greenish and yellowish tones.

 

Ultraviolet Light [f/8 for 1/160” @ ISO 400 with SB-14 UV-modified Flash and Baader UV-Pass Filter]

 

Ultraviolet Light [f/8 for 1/160” @ ISO 400 with SB-14 UV-modified Flash and Baader UV-Pass Filter]