North America Native Plant

Snake Milkvetch

Botanical name: Astragalus iodanthus var. diaphanoides

USDA symbol: ASIOD

Life cycle: perennial

Habit: forb

Native status: Native to the lower 48 states  

Synonyms: Astragalus iodanthus S. Watson var. vipereus Barneby (ASIOV)   

Snake Milkvetch: A Hidden Gem for Western Native Plant Gardens If you’re looking to add something truly unique to your native plant collection, snake milkvetch (Astragalus iodanthus var. diaphanoides) might just be the conversation starter your garden needs. This perennial wildflower is one of those plants that makes fellow native ...

Snake Milkvetch: A Hidden Gem for Western Native Plant Gardens

If you’re looking to add something truly unique to your native plant collection, snake milkvetch (Astragalus iodanthus var. diaphanoides) might just be the conversation starter your garden needs. This perennial wildflower is one of those plants that makes fellow native plant enthusiasts do a double-take – partly because of its intriguing name, and partly because it’s genuinely uncommon in cultivation.

What Is Snake Milkvetch?

Snake milkvetch belongs to the legume family and is a perennial plant native to the western United States. Like many members of the Astragalus genus, it’s part of a large group of plants commonly called milkvetches or locoweeds. Don’t let the snake in the name worry you – it’s perfectly harmless to gardeners and likely earned its common name from some aspect of its appearance or growth pattern.

You might also see this plant referenced by its botanical synonym, Astragalus iodanthus var. vipereus, in older botanical references.

Where Does Snake Milkvetch Grow?

This native beauty calls the American West home, specifically thriving in Idaho, Nevada, and Oregon. As a plant adapted to these regions, it’s naturally suited to the unique growing conditions found in the western states.

Should You Grow Snake Milkvetch?

Here’s where things get interesting – and a bit challenging. Snake milkvetch is what you might call a specialist’s plant. While it’s undoubtedly a legitimate native species that would make a fascinating addition to the right garden, there are some practical considerations:

  • It’s extremely rare in the nursery trade
  • Limited growing information is available for home gardeners
  • Seeds or plants are difficult to source responsibly
  • Specific growing requirements are not well-documented

That said, if you can source it responsibly and you’re an experienced native plant gardener who enjoys a challenge, snake milkvetch could be a remarkable addition to a specialized western native plant collection.

Growing Conditions and Care

While specific information about this variety’s exact preferences is limited, we can make some educated guesses based on its native range and the general characteristics of western Astragalus species:

  • Likely prefers well-draining soils
  • Probably drought-tolerant once established
  • May prefer full sun to partial shade
  • Suited for USDA hardiness zones typical of its native range (likely zones 4-8)

As a perennial, snake milkvetch should return year after year once established, making it a potentially valuable long-term addition to your native plant landscape.

Garden Design Considerations

Given its rarity and specialized nature, snake milkvetch would be best suited for:

  • Dedicated native plant gardens
  • Rock gardens or xeriscapes
  • Plant collector’s gardens
  • Educational or botanical garden settings

This isn’t a plant for mass plantings or typical residential landscapes, but rather a special specimen for gardeners who appreciate botanical diversity and rarity.

A Word of Caution

If you’re interested in growing snake milkvetch, please ensure you source seeds or plants from reputable native plant nurseries or seed companies that collect responsibly. Given its apparent rarity, wild collection should be avoided entirely.

Alternative Native Options

If snake milkvetch proves too elusive or challenging, consider these more readily available native alternatives from the same region:

  • Other Astragalus species native to your specific area
  • Lupinus species (lupines)
  • Penstemon species (beardtongues)
  • Regional native wildflower mixes

Snake milkvetch represents the fascinating diversity of our native flora – even if it’s not the easiest plant to grow, knowing it exists reminds us of the incredible botanical treasures hidden in our western landscapes. Whether you end up growing it or simply appreciating it from afar, plants like snake milkvetch inspire us to look more closely at the natural world around us.

Snake 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 iodanthus S. Watson - Humboldt River milkvetch

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