North America Native Plant

Silverleaf Milkvetch

Botanical name: Astragalus argophyllus var. stocksii

USDA symbol: ASARS

Life cycle: perennial

Habit: forb

Native status: Native to the lower 48 states  

Synonyms: Astragalus henrimontanensis S.L. Welsh (ASHE6)  âš˜  Astragalus stocksii S.L. Welsh, non Benth. ex Bunge (ASST8)   

Silverleaf Milkvetch: A Rare Native Gem Worth Knowing Meet the silverleaf milkvetch (Astragalus argophyllus var. stocksii), a fascinating native perennial that’s definitely not your garden-variety plant. This member of the legume family calls the American Southwest home, and while it may not be the showiest plant in the neighborhood, it ...

Rare plant alert!

Region: Conservation status by state

Status: S5T2T3Q: Status is uncertain but is somewhere between the following rankings: Uncertain taxonomy: ⚘ Subspecies or variety is imperiled: Extremely rare due to factor(s) making it especially vulnerable to extinction. Typically 6 to 20 occurrences or few remaining individuals (1,000 to 3,000) ⚘ Subspecies or variety is vulnerable: Either very rare and local throughout its range, found only in a restricted range (even if abundant at some locations), or factors are making it vulnerable to extinction. Typically 21 to 100 occurrences or between 3,000 and 10,000 individuals. ⚘ Secure: At very low or no risk of extinction in the jurisdiction due to a very extensive range, abundant populations or occurrences, with little to no concern from declines or threats. ⚘ Uncertain taxonomy: ⚘ Imperiled: Extremely rare due to factor(s) making it especially vulnerable to extinction. Typically 6 to 20 occurrences or few remaining individuals (1,000 to 3,000) ⚘ Vulnerable: Either very rare and local throughout its range, found only in a restricted range (even if abundant at some locations), or factors are making it vulnerable to extinction. Typically 21 to 100 occurrences or between 3,000 and 10,000 individuals ⚘

Region: Conservation status by state

Silverleaf Milkvetch: A Rare Native Gem Worth Knowing

Meet the silverleaf milkvetch (Astragalus argophyllus var. stocksii), a fascinating native perennial that’s definitely not your garden-variety plant. This member of the legume family calls the American Southwest home, and while it may not be the showiest plant in the neighborhood, it carries the special distinction of being a true regional native with a story worth telling.

Where Does Silverleaf Milkvetch Call Home?

This particular variety of milkvetch has carved out its niche in just two states: Arizona and Utah. As a native plant of the lower 48 states, it has spent countless generations adapting to the unique conditions of the southwestern landscape. Its limited geographic range makes it a true regional specialty – think of it as the botanical equivalent of a local artisanal cheese!

The Name Game

Botanists love their alternative names, and silverleaf milkvetch is no exception. You might also see it listed as Astragalus henrimontanensis or Astragalus stocksii in older references, but these are considered synonyms of our current accepted name.

Why Consider This Native Plant?

Here’s where things get interesting – and a bit challenging. Silverleaf milkvetch appears to be quite rare, which makes it both intriguing and problematic for home gardeners. On one hand, growing native plants is always a win for local ecosystems. Native plants have co-evolved with local wildlife, soil conditions, and climate patterns, making them naturally suited to their home regions.

However, the rarity of this particular variety means we need to be extra thoughtful about how we approach it.

The Gardener’s Dilemma

Unfortunately, detailed growing information for this specific variety is quite limited. We know it’s a perennial, which means it should return year after year once established – always a plus in the gardening world. But beyond that, the specifics of its growing conditions, care requirements, and landscape uses remain somewhat mysterious.

This lack of readily available information isn’t necessarily a bad thing – it often indicates a plant that’s either very specialized in its habitat needs or simply hasn’t been widely cultivated.

A Word About Responsible Gardening

Given the apparent rarity of silverleaf milkvetch, any gardener interested in this plant should prioritize responsible sourcing. This means:

  • Never collecting plants from wild populations
  • Purchasing only from reputable native plant nurseries
  • Ensuring any plant material comes from ethically propagated sources
  • Supporting conservation efforts for rare native plants

Alternative Native Options

If you’re drawn to the idea of growing native milkvetches but can’t locate silverleaf milkvetch, consider exploring other Astragalus species that might be more readily available and better documented for your region. Many milkvetches share similar ecological benefits and can provide food sources for native pollinators and wildlife.

The Bottom Line

Silverleaf milkvetch represents the fascinating complexity of native plant conservation and gardening. While we may not have all the answers about growing this particular variety, its story reminds us of the incredible diversity of plants that call our landscapes home – and the importance of protecting and understanding these botanical treasures.

For most gardeners, this might be more of a plant to know about rather than a plant to grow, but for dedicated native plant enthusiasts with access to responsibly sourced material, it could be a unique addition to a specialized collection focused on southwestern natives.

Silverleaf Milkvetch

Classification

Group

Dicot

Kingdom

Plantae - Plants

Subkingdom

Tracheobionta - Vascular plants

Superdivision

Spermatophyta - Seed plants

Division

Magnoliophyta - Flowering plants

Subdivision
Class

Magnoliopsida - Dicotyledons

Subclass

Rosidae

Order

Fabales

Family

Fabaceae Lindl. - Pea family

Genus

Astragalus L. - milkvetch

Species

Astragalus argophyllus Nutt. - silverleaf milkvetch

Plant data source: USDA, NRCS 2025. The PLANTS Database. https://plants.usda.gov,. 2/25/2025. National Plant Data Team, Greensboro, NC USA