North America Native Plant

Duane’s Milkvetch

Botanical name: Astragalus pinonis var. atwoodii

USDA symbol: ASPIA

Life cycle: perennial

Habit: forb

Native status: Native to the lower 48 states  

Synonyms: Astragalus atwoodii S.L. Welsh & Thorne (ASAT4)   

Duane’s Milkvetch: A Rare Arizona Treasure Worth Preserving If you’re passionate about native plants and conservation gardening, you might want to learn about Duane’s milkvetch (Astragalus pinonis var. atwoodii), one of Arizona’s botanical gems. This perennial member of the pea family represents something special in the world of native gardening ...

Rare plant alert!

Region: Conservation status by state

Status: S2S3T1: Status is uncertain but is somewhere between the following rankings: Subspecies or variety is critically Imperiled: Extremely rare due to factor(s) making it especially vulnerable to extinction. Typically 5 or fewer occurrences or very few remaining individuals (<1,000) ⚘ 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 ⚘

Duane’s Milkvetch: A Rare Arizona Treasure Worth Preserving

If you’re passionate about native plants and conservation gardening, you might want to learn about Duane’s milkvetch (Astragalus pinonis var. atwoodii), one of Arizona’s botanical gems. This perennial member of the pea family represents something special in the world of native gardening – a plant that’s both beautiful and rare, requiring our careful stewardship.

What Makes Duane’s Milkvetch Special?

Duane’s milkvetch is a true Arizona native, found nowhere else in the world except within the state’s borders. This makes it what botanists call an endemic species – a plant that has evolved to thrive in very specific conditions and locations. The plant is also known by its scientific synonym, Astragalus atwoodii, named after botanist Duane Atwood.

As a perennial, this hardy little plant returns year after year once established, though getting it to that point can be quite the gardening adventure!

Where Does It Grow?

This milkvetch calls Arizona home, specifically thriving in the Colorado Plateau region of the state. Its natural habitat consists of sandy washes, rocky slopes, and desert grasslands where few other plants dare to grow.

Important Conservation Note

Here’s something crucial to know: Duane’s milkvetch has a conservation status of S2S3T1, which means it’s considered rare and potentially vulnerable in the wild. This rarity status is a big deal – it tells us this plant needs our help to survive for future generations.

If you’re interested in growing this species, please only obtain seeds or plants from reputable, ethical sources that don’t harvest from wild populations. Better yet, consider supporting conservation organizations working to protect this species in its natural habitat.

Garden Appeal and Design Role

Despite its rarity, Duane’s milkvetch offers some lovely garden qualities for those up for the challenge. The plant produces charming purple to pink pea-like flowers that add a delicate splash of color to desert landscapes. Its silvery-green compound leaves provide an attractive backdrop and help it blend beautifully with other drought-tolerant natives.

This milkvetch works best in:

  • Rock gardens that mimic its natural rocky habitat
  • Desert and xeriscape gardens
  • Conservation collections and botanical gardens
  • Specialized native plant displays

Pollinator and Wildlife Benefits

Like other members of the pea family, Duane’s milkvetch supports pollinators by providing nectar and pollen for native bees and other beneficial insects. Every flower that blooms helps sustain the local ecosystem – another great reason to consider conservation gardening with rare natives like this one.

Growing Conditions and Care

Fair warning: this isn’t a beginner’s plant! Duane’s milkvetch has very specific needs that mirror its harsh natural environment:

  • Soil: Excellent drainage is absolutely critical – think sandy or rocky soils that dry out quickly
  • Sun: Full sun exposure, just like in its desert home
  • Water: Drought tolerant once established, but getting it established can be tricky
  • Climate: Suitable for USDA hardiness zones 5-8, with hot, dry summers and cold winters

Planting and Care Tips

If you decide to take on the challenge of growing Duane’s milkvetch, here are some tips for success:

  • Plant in spring after the last frost, giving roots time to establish before summer heat
  • Create a planting mix with lots of coarse sand, gravel, or pumice for drainage
  • Water sparingly – overwatering is more likely to kill this plant than drought
  • Be patient – establishment can take time, and the plant may not bloom for a year or two
  • Avoid fertilizing, as desert plants typically prefer lean soils

Should You Grow It?

Duane’s milkvetch isn’t for every gardener or every garden. It’s a specialized plant that requires specific conditions and a commitment to conservation ethics. However, for experienced native plant gardeners who want to contribute to conservation efforts, it can be a rewarding challenge.

If you’re just starting your native gardening journey, consider beginning with more common Arizona natives like desert marigold, penstemon species, or brittlebush. These will give you experience with desert gardening techniques while you decide if you’re ready to take on rare species cultivation.

Remember, every rare plant we successfully grow in cultivation is a small victory for conservation – but only when we do it responsibly and ethically. Happy gardening, and thank you for considering the preservation of Arizona’s unique botanical heritage!

Duane’s 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 pinonis M.E. Jones - pinyon milkvetch

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