North America Native Plant

Owyhee Milkvetch

Botanical name: Astragalus atratus var. owyheensis

USDA symbol: ASATO

Life cycle: perennial

Habit: forb

Native status: Native to the lower 48 states  

Synonyms: Astragalus owyheensis A. Nelson & J.F. Macbr. (ASOW)   

Owyhee Milkvetch: A Hardy Native for Western Gardens Meet Owyhee milkvetch (Astragalus atratus var. owyheensis), a tough little perennial that’s perfectly at home in the arid landscapes of the American West. This unassuming native might not win any flashy flower contests, but what it lacks in showiness, it more than ...

Rare plant alert!

Region: Conservation status by state

Status: S4S5T3: Status is uncertain but is somewhere between the following rankings: 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. ⚘ Apparently Secure: Uncommon but not rare, and usually widespread. Possibly cause for longterm concern. Typically more than 100 occurrences in the state or more than 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. ⚘

Owyhee Milkvetch: A Hardy Native for Western Gardens

Meet Owyhee milkvetch (Astragalus atratus var. owyheensis), a tough little perennial that’s perfectly at home in the arid landscapes of the American West. This unassuming native might not win any flashy flower contests, but what it lacks in showiness, it more than makes up for in resilience and ecological value.

Where Does Owyhee Milkvetch Call Home?

True to its name, Owyhee milkvetch is native to the Owyhee region and surrounding areas, naturally occurring across Idaho, Nevada, and Oregon. You’ll find this hardy perennial thriving in sagebrush steppe and desert environments, where it has adapted to survive scorching summers and frigid winters with equal aplomb.

What Does It Look Like?

Don’t expect this plant to dominate your garden with bold, attention-grabbing blooms. Owyhee milkvetch is more of the quiet beauty type. It produces delicate, pea-like flowers in shades of purple to pink, typical of plants in the legume family. The compound leaves give it a soft, feathery appearance that adds subtle texture to native plantings.

Why Plant Owyhee Milkvetch?

Here’s where this little plant really shines:

  • Drought champion: Once established, it thrives with minimal water—perfect for water-wise gardening
  • Pollinator magnet: Native bees and other pollinators appreciate its nectar-rich flowers
  • Low maintenance: Plant it and largely forget about it—this perennial knows how to take care of itself
  • Ecological authenticity: Support native ecosystems by choosing plants that belong in your region
  • Soil improvement: As a legume, it can fix nitrogen in the soil, benefiting neighboring plants

Growing Owyhee Milkvetch Successfully

The good news is that if you live within its native range (roughly USDA hardiness zones 4-8), growing Owyhee milkvetch is refreshingly straightforward:

Sun and Soil: Give it full sun and well-draining soil. This plant absolutely despises wet feet, so avoid heavy clay or areas that stay soggy.

Watering: Water regularly the first year to help establish roots, then back off significantly. Mature plants are incredibly drought-tolerant and prefer the tough love approach to irrigation.

Maintenance: Minimal pruning needed. You might allow it to self-seed for a more naturalized look, or deadhead spent flowers if you prefer a tidier appearance.

Where to Use It in Your Landscape

Owyhee milkvetch works beautifully in:

  • Native plant gardens
  • Drought-tolerant landscapes
  • Naturalized areas
  • Rock gardens
  • Pollinator gardens

A Word of Caution About Sourcing

Here’s the catch: Owyhee milkvetch isn’t your typical garden center find. If you’re interested in adding this native to your landscape, you’ll need to seek out specialized native plant nurseries or participate in native seed collection programs. Always ensure you’re sourcing plants or seeds responsibly and legally.

The Bottom Line

Owyhee milkvetch might not be the star of your garden show, but it’s the reliable supporting cast member that makes everything else look better. If you’re gardening in its native range and want to create habitat for pollinators while conserving water, this hardy little perennial deserves a spot in your landscape. Just don’t expect it to be high-maintenance—this plant prefers to be left alone to do what it does best: survive and thrive in tough conditions.

Owyhee 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 atratus S. Watson - mourning milkvetch

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