North America Native Plant

Siskiyou Milkvetch

Botanical name: Astragalus whitneyi var. siskiyouensis

USDA symbol: ASWHS

Life cycle: perennial

Habit: forb

Native status: Native to the lower 48 states  

Synonyms: Astragalus whitneyi A. Gray ssp. siskiyouensis (Rydb.) Abrams (ASWHS3)   

Siskiyou Milkvetch: A Hidden Gem for Pacific Northwest Native Gardens If you’re looking to add some authentic Pacific Northwest charm to your garden, meet the Siskiyou milkvetch (Astragalus whitneyi var. siskiyouensis). This delightful native perennial might not be a household name, but it’s definitely worth getting to know – especially ...

Rare plant alert!

Region: Conservation status by state

Status: S5T3T4: 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. ⚘ Subspecies or varieties is apparently secure: Uncommon but not rare, and usually widespread. Possibly cause for longterm concern. Typically more than 100 occurrences in the region 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. ⚘

Siskiyou Milkvetch: A Hidden Gem for Pacific Northwest Native Gardens

If you’re looking to add some authentic Pacific Northwest charm to your garden, meet the Siskiyou milkvetch (Astragalus whitneyi var. siskiyouensis). This delightful native perennial might not be a household name, but it’s definitely worth getting to know – especially if you’re passionate about supporting local ecosystems and creating low-maintenance, drought-tolerant landscapes.

What Makes Siskiyou Milkvetch Special?

The Siskiyou milkvetch is a true regional native, calling the Siskiyou Mountains of California and Oregon home. As a member of the legume family, this perennial brings both beauty and ecological benefits to your garden. Its charming purple to pink pea-like flowers bloom against silvery-green compound leaves, creating a subtle yet eye-catching display that feels perfectly at home in the Pacific Northwest landscape.

Where You’ll Find It Growing Wild

This special variety is endemic to California and Oregon, specifically thriving in the unique conditions of the Siskiyou Mountains region. It’s adapted to the Mediterranean climate patterns and rocky soils that characterize this bioregion.

Why Consider Planting Siskiyou Milkvetch?

There are several compelling reasons to include this native beauty in your garden:

  • Authentic regional character: It’s genuinely native to the Pacific Northwest, supporting local biodiversity
  • Pollinator magnet: The nectar-rich flowers attract native bees and butterflies
  • Low maintenance: Once established, it’s incredibly drought tolerant
  • Unique aesthetic: Offers a different texture and form compared to common garden plants
  • Soil improvement: Like other legumes, it fixes nitrogen in the soil

Important Conservation Note

Before you rush out to find this plant, there’s something important to know: Siskiyou milkvetch has a conservation status that suggests some level of rarity or concern. If you decide to grow this species, please make sure you source it responsibly from reputable native plant nurseries rather than collecting from wild populations. This helps ensure wild communities remain healthy while still allowing you to enjoy this special plant in your garden.

Perfect Garden Settings

Siskiyou milkvetch shines in several types of garden settings:

  • Rock gardens: Its compact form and drought tolerance make it ideal for rocky, well-drained spots
  • Native plant gardens: A perfect addition to regional native plant collections
  • Xeriscapes: Excellent for water-wise landscaping projects
  • Naturalized areas: Great for creating authentic Pacific Northwest plant communities

Growing Conditions and Care

The key to success with Siskiyou milkvetch is understanding its mountain origins. This plant thrives in conditions that mimic its natural habitat:

  • Sunlight: Full sun to partial shade
  • Soil: Well-drained soils are absolutely essential – think rocky, gravelly, or sandy conditions
  • Water: Drought tolerant once established, but needs occasional water during extreme dry spells
  • Climate zones: Hardy in USDA zones 6-8, perfect for most Pacific Northwest gardens

Planting and Care Tips

Growing Siskiyou milkvetch successfully requires some specific considerations:

  • Drainage is everything: Poor drainage is the quickest way to lose this plant. Amend heavy soils with gravel or sand
  • Plant young: Like many native legumes, it develops a deep taproot and doesn’t transplant well once established
  • Go easy on the water: Overwatering is more dangerous than underwatering for this drought-adapted species
  • Minimal fertilizer: As a nitrogen-fixing legume, it doesn’t need rich soils and may actually struggle in overly fertile conditions
  • Be patient: Native perennials often take a season or two to become fully established

The Bottom Line

Siskiyou milkvetch might not be the flashiest plant in your garden, but it offers something increasingly valuable: authentic regional character combined with ecological benefits. If you’re gardening in California or Oregon and want to support local wildlife while creating a beautiful, low-maintenance landscape, this native gem deserves a spot in your garden. Just remember to source it responsibly and give it the well-drained conditions it craves. Your local pollinators – and the broader ecosystem – will thank you for it.

Siskiyou 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 whitneyi A. Gray - balloonpod milkvetch

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