North America Native Plant

Jepson’s Milkvetch

Botanical name: Astragalus rattanii var. jepsonianus

USDA symbol: ASRAJ

Life cycle: annual

Habit: forb

Native status: Native to the lower 48 states  

Jepson’s Milkvetch: A Mysterious California Native If you’re a native plant enthusiast always on the hunt for something truly unique, you might have stumbled across the name Jepson’s milkvetch. This California annual is part of the fascinating Astragalus genus, but here’s the thing – it’s wrapped in quite a bit ...

Rare plant alert!

Region: Conservation status by state

Status: S4T3: 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 ⚘

Jepson’s Milkvetch: A Mysterious California Native

If you’re a native plant enthusiast always on the hunt for something truly unique, you might have stumbled across the name Jepson’s milkvetch. This California annual is part of the fascinating Astragalus genus, but here’s the thing – it’s wrapped in quite a bit of mystery.

What We Know About Jepson’s Milkvetch

Jepson’s milkvetch (Astragalus rattanii var. jepsonianus) is an annual plant native to California. As a member of the legume family, it likely shares the nitrogen-fixing abilities that make many of its cousins so valuable in natural ecosystems. However, this particular variety is quite elusive in terms of detailed documentation.

Where Does It Grow?

This native plant calls California home, though specific distribution details within the state remain unclear. Like many California natives, it has likely adapted to the state’s Mediterranean climate and diverse microclimates.

A Word of Caution: Rarity Matters

Here’s where things get important for responsible gardeners. Jepson’s milkvetch has a conservation status of S4T3, which suggests it may have limited distribution or population concerns. This means if you’re ever fortunate enough to encounter this plant or find seeds available, it’s crucial to ensure they come from ethical, responsible sources.

Never collect seeds or plants from wild populations, especially when dealing with potentially rare varieties. Instead, work with reputable native plant societies or specialized nurseries that practice sustainable propagation.

Should You Try Growing It?

The honest answer? It’s complicated. With so little information available about this specific variety’s growing requirements, success would likely require some experimentation. As an annual, it would complete its entire life cycle in one growing season, but without knowing its specific needs for germination, water, soil type, or sun exposure, it could be a challenging project.

Better-Known Alternatives

If you’re drawn to the idea of growing a native California milkvetch, consider these better-documented relatives:

  • Purple milkvetch (Astragalus purpureus) – easier to find and grow
  • Locoweed milkvetch (Astragalus lentiginosus) – more widely available
  • Other native California legumes like lupines or clovers

The Bottom Line

Jepson’s milkvetch represents one of those intriguing gaps in our native plant knowledge. While we can’t provide a complete growing guide, its story reminds us that California’s flora still holds mysteries waiting to be better understood. If you’re interested in this plant, consider supporting botanical research or native plant conservation efforts that help document and protect these lesser-known species.

Sometimes the most valuable thing we can do as native plant gardeners is simply appreciate that not every species needs to be in our gardens – some are perfectly content remaining wild and mysterious.

Jepson’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 rattanii A. Gray - Rattan's milkvetch

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