North America Native Plant

Fish Slough Milkvetch

Botanical name: Astragalus lentiginosus var. piscinensis

USDA symbol: ASLEP3

Life cycle: perennial

Habit: forb

Native status: Native to the lower 48 states  

Fish Slough Milkvetch: A Rare California Native Worth Protecting Meet the Fish Slough milkvetch, a small but mighty perennial that’s become one of California’s most treasured botanical rarities. This unassuming legume might not win any flashy flower contests, but its story of survival and conservation makes it absolutely fascinating for ...

Rare plant alert!

Region: United States

Status: S5T1: 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) ⚘ 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. ⚘ Threatened: Experiencing significant population decline or habitat loss that could lead to its endangerment if not addressed. ⚘

Region: United States

Fish Slough Milkvetch: A Rare California Native Worth Protecting

Meet the Fish Slough milkvetch, a small but mighty perennial that’s become one of California’s most treasured botanical rarities. This unassuming legume might not win any flashy flower contests, but its story of survival and conservation makes it absolutely fascinating for native plant enthusiasts.

What Makes This Plant Special?

The Fish Slough milkvetch (Astragalus lentiginosus var. piscinensis) is what botanists call an endemic species – meaning it exists naturally in only one tiny corner of the world. In this case, that corner happens to be the Fish Slough area in Mono County, California. Talk about being picky about your neighborhood!

This perennial native produces delicate purple-pink flowers that look like tiny sweet peas, which makes sense since it’s part of the legume family. The compound leaves give it a soft, feathery appearance that contrasts beautifully with the harsh desert landscape it calls home.

Where Does It Grow?

You won’t find this little gem just anywhere in California – it’s exclusively native to a very specific area around Fish Slough in the eastern Sierra Nevada region. This incredibly limited distribution is part of what makes it so special and, unfortunately, so vulnerable.

Important Conservation Status

Here’s something crucial to know: The Fish Slough milkvetch is listed as Threatened by the U.S. Fish and Wildlife Service. Its Global Conservation Status is S5T1, indicating it’s critically imperiled. This means if you’re interested in growing this plant, you absolutely must source it responsibly from reputable native plant nurseries or conservation organizations.

Please never collect seeds or plants from wild populations – every individual in the wild is precious for the species’ survival.

Should You Grow It?

If you’re passionate about conservation and have experience with challenging native plants, the Fish Slough milkvetch can be a meaningful addition to a specialized native garden. However, this isn’t a plant for beginners or casual gardeners. Here’s why you might want to consider it:

  • You’re contributing to conservation efforts by maintaining genetic diversity
  • It attracts native pollinators, especially specialized bees
  • It’s a conversation starter about California’s rare flora
  • It connects your garden to a unique ecological story

Growing Conditions

This milkvetch is adapted to very specific conditions that mirror its native Fish Slough habitat:

  • Soil: Alkaline, well-draining soils (it actually prefers what most plants would consider poor soil)
  • Water: Minimal irrigation once established – this plant thrives on neglect
  • Sun: Full sun exposure
  • Climate: High desert conditions, likely hardy in USDA zones 7-9
  • Drainage: Excellent drainage is absolutely critical

Planting and Care Tips

Growing Fish Slough milkvetch successfully means recreating a slice of the Mojave Desert:

  • Plant in a raised bed or slope to ensure perfect drainage
  • Amend heavy soils with sand and gravel, not compost
  • Water sparingly – overwatering is the quickest way to kill this plant
  • Avoid fertilizers, as this species is adapted to nutrient-poor soils
  • Provide protection from wet winter conditions if you live in a rainy climate

The Bottom Line

The Fish Slough milkvetch isn’t for everyone, but for dedicated native plant gardeners and conservation enthusiasts, it represents something precious – a living link to California’s unique ecological heritage. If you choose to grow it, you’re not just adding a plant to your garden; you’re participating in conservation efforts for one of the Golden State’s rarest natives.

Remember: only source this plant from reputable suppliers, never from the wild, and consider it a long-term commitment to conservation gardening. Sometimes the smallest plants carry the biggest responsibilities!

Fish Slough 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 lentiginosus Douglas ex Hook. - freckled milkvetch

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