Tiny Plants Make Tiny Seeds

by Jul 24, 2024Education

seeds collected against a ruler to show their small size
As we continue into the heat of the summer, plants are beginning to share their seeds for future planting. 

We recently completed a successful seed collection trip for one of our smallest microflora species: Sentry Milkvetch (Astragalus cremnophylax). Small but mighty, the Sentry Milkvetch is a member of the Pea family, and it is only grown from the Kaibab limestone rim of the Grand Canyon. 

The translation of the Latin name loosely refers to the plant as being the Sentinel or the Watchman of the Gorge–aptly named as it lines the edges of the Grand Canyon, standing watch over the vast valley. 

This rare plant was listed as Endangered in 1990 at a time when there were only a few populations known from the South Rim. Recently, new populations have been discovered on the North Rim–exciting news for the future of this tiny plant! These populations had not yet had any seed banking activity, offering the Arboretum an opportunity to serve the Colorado Plateau beyond the acres of our gardens. 

Golden Columbine blooming at The Arb.
Sentry Milkvetch
(
Astragalus cremnophylax)
Picture of Arb employee collecting seeds at the Canyon.
Horticulturist Gina Goegan making it look easy as she collects seeds from Astragalus cremnophylax.

Supported by the U.S. Fish and Wildlife Service and the Grand Canyon National Park, The Arboretum at Flagstaff was tasked with making conservation collections for many of these new populations. While this endeavor proved to be a challenge, we managed to preserve just over four hundred seeds from only four populations! As you can see in the photo, this tiny plant sure does make some tiny seeds! 

What makes this collection particularly difficult is the fact that they are so small, there is danger in trampling neighboring plants as collectors tip-toe across the limestone bedrock to gather seeds smaller than a grain of rice. 

Most of the seed will be stored for long-term storage as part of our work with the Center for Plant Conservation. Some of the seed will be reserved at the Arboretum for germination testing to see how viable they are. The resulting individual plants will be held on display at The Arboretum at Flagstaff in our Horticulture Center Greenhouse.

Sheila C. Murray is Conservation Botanist at The Arboretum at Flagstaff.

Sheila Murray