North America Native Plant

Woolly Locoweed

Botanical name: Astragalus mollissimus var. bigelovii

USDA symbol: ASMOB

Life cycle: perennial

Habit: forb

Native status: Native to the lower 48 states  

Synonyms: Astragalus bigelovii A. Gray (ASBI8)  âš˜  Astragalus bigelovii A. Gray var. typicus Barneby (ASBIT)   

Woolly Locoweed: A Beautiful but Dangerous Native You Should Avoid in Your Garden When it comes to native plants, we usually encourage gardeners to embrace species indigenous to their region. However, woolly locoweed (Astragalus mollissimus var. bigelovii) is one stunning native that comes with a serious warning label. While this ...

Woolly Locoweed: A Beautiful but Dangerous Native You Should Avoid in Your Garden

When it comes to native plants, we usually encourage gardeners to embrace species indigenous to their region. However, woolly locoweed (Astragalus mollissimus var. bigelovii) is one stunning native that comes with a serious warning label. While this perennial wildflower is undeniably beautiful with its silvery foliage and delicate purple blooms, it’s earned its ominous locoweed moniker for good reason.

What Is Woolly Locoweed?

Woolly locoweed is a native perennial plant that belongs to the legume family. Also known by its synonyms Astragalus bigelovii, this southwestern native has adapted perfectly to harsh desert conditions. The woolly part of its name comes from the plant’s distinctive silvery-white, fuzzy foliage that helps it conserve moisture in arid environments.

Where Does Woolly Locoweed Grow?

This hardy perennial is native to the southwestern United States, specifically thriving in Arizona, New Mexico, and Texas. It’s perfectly adapted to the challenging conditions of the American Southwest, where it grows naturally in desert grasslands and scrublands.

Why the Warning About This Native Plant?

Here’s where things get serious: woolly locoweed contains toxic alkaloids that can poison livestock and potentially harm humans. The loco in locoweed refers to the erratic behavior animals exhibit when they consume this plant. Chronic consumption can lead to:

  • Neurological damage in livestock
  • Reproductive problems
  • Death in severe cases
  • Potential toxicity to pets and humans

For this reason, we strongly advise against planting woolly locoweed in home gardens, especially if you have pets, livestock, or small children who might come into contact with the plant.

Ecological Value (From a Safe Distance)

Despite its toxicity, woolly locoweed does play an important role in its native ecosystem. The plant’s purple to pink pea-like flowers attract native pollinators, including bees and butterflies. In the wild, it serves as part of the complex desert food web, though most wildlife instinctively avoid consuming it due to its toxicity.

Growing Conditions (For Educational Purposes Only)

While we don’t recommend cultivating this plant, understanding its natural growing requirements helps us appreciate its desert adaptations:

  • USDA Hardiness Zones: 7-10
  • Soil: Well-drained, sandy or rocky desert soils
  • Water: Extremely drought-tolerant once established
  • Sun: Full sun exposure
  • Climate: Arid, low-humidity conditions

Safe Native Alternatives for Southwestern Gardens

If you’re drawn to the silvery foliage and purple flowers of woolly locoweed, consider these safe native alternatives for your southwestern garden:

  • Desert marigold (Baileya multiradiata) – bright yellow flowers, drought-tolerant
  • Penstemon species – tubular flowers beloved by hummingbirds
  • Desert lupine (Lupinus arizonicus) – similar purple pea-like flowers, less toxic
  • Brittlebush (Encelia farinosa) – silvery foliage with yellow daisy-like flowers

The Bottom Line

Woolly locoweed serves as a perfect reminder that not all native plants are suitable for home cultivation. While we celebrate its role in natural ecosystems and admire its desert adaptations, this is one native species best appreciated from afar. If you encounter it in the wild during desert hikes, enjoy its beauty but keep your distance – and definitely keep your pets away.

Remember, being a responsible native plant gardener means choosing species that are not only appropriate for your region but also safe for your family, pets, and community. There are plenty of other stunning southwestern natives that can give you that desert garden aesthetic without the safety concerns!

Woolly Locoweed

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 mollissimus Torr. - woolly locoweed

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