North America Native Plant

Sentry Milkvetch

Botanical name: Astragalus cremnophylax var. cremnophylax

USDA symbol: ASCRC4

Life cycle: perennial

Habit: forb

Native status: Native to the lower 48 states  

Sentry Milkvetch: A Rare Desert Gem Worth Protecting Meet the sentry milkvetch (Astragalus cremnophylax var. cremnophylax), one of Arizona’s most endangered botanical treasures. This tiny perennial legume might not be destined for your backyard garden, but its story is absolutely worth telling – and its conservation is worth supporting. What ...

Rare plant alert!

Region: United States

Status: S1S2T1: Status is uncertain but is somewhere between the following rankings: 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) ⚘ 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) ⚘ Imperiled: Extremely rare due to factor(s) making it especially vulnerable to extinction. Typically 6 to 20 occurrences or few remaining individuals (1,000 to 3,000) ⚘ Endangered: In danger of extinction throughout all or a significant portion of its range. ⚘

Region: United States

Sentry Milkvetch: A Rare Desert Gem Worth Protecting

Meet the sentry milkvetch (Astragalus cremnophylax var. cremnophylax), one of Arizona’s most endangered botanical treasures. This tiny perennial legume might not be destined for your backyard garden, but its story is absolutely worth telling – and its conservation is worth supporting.

What Makes Sentry Milkvetch Special?

Sentry milkvetch is a true Arizona native, found nowhere else in the world except for a few precarious cliff faces in the Grand Canyon State. This remarkable little plant has earned its sentry nickname by standing guard on limestone cliffs, where it has adapted to some of the harshest growing conditions imaginable.

The plant produces delicate purple-pink pea-like flowers that seem almost impossibly cheerful considering the tough environment they call home. As a member of the legume family, it shares relatives with more familiar plants like beans and peas, but this desert dweller has evolved some pretty impressive survival skills.

Where Does Sentry Milkvetch Grow?

Sentry milkvetch is found exclusively in Arizona, where it clings to life on limestone cliffs and rocky outcrops. Its distribution is so limited that you could probably visit all of its known locations in a single day – if you were an experienced rock climber, that is!

Why You Shouldn’t (and Can’t) Grow It

Here’s where we need to have a serious conversation. Sentry milkvetch is listed as endangered, with a conservation status that basically translates to extremely rare and at risk of extinction. This isn’t a plant you can or should try to grow in your garden, and here’s why:

  • It’s protected by law: As an endangered species, collecting or disturbing sentry milkvetch is illegal
  • Impossible growing conditions: It requires specific limestone cliff habitats that can’t be replicated in typical gardens
  • Conservation priority: Every wild plant needs to stay where it is to help the species survive
  • Specialized needs: This plant has evolved for extreme drainage and desert conditions that would kill most other plants

How You Can Help Instead

Just because you can’t grow sentry milkvetch doesn’t mean you can’t support it! Here are some meaningful ways to contribute to its conservation:

  • Support organizations working on rare plant conservation in Arizona
  • Choose other native Arizona plants for your desert garden
  • Learn about and share information about endangered plants in your area
  • Practice responsible hiking and respect protected plant habitats

Native Alternatives for Your Arizona Garden

While you can’t have sentry milkvetch, Arizona offers plenty of other beautiful native legumes that will thrive in desert gardens:

  • Desert broom (Psorothamnus scoparius)
  • Fairy duster (Calliandra eriophylla)
  • Desert ironwood (Olneya tesota)
  • Blue palo verde (Parkinsonia florida)

These alternatives will give you those lovely pea-family flowers while supporting local pollinators and wildlife – all without putting pressure on endangered species.

The Bigger Picture

Sentry milkvetch reminds us that not every native plant is meant for cultivation, and that’s perfectly okay. Some plants serve their most important role by simply existing in their wild habitats, maintaining genetic diversity and ecosystem balance. By respecting these boundaries and choosing appropriate alternatives, we can be better stewards of our native plant heritage.

The next time you’re hiking in Arizona’s desert landscape, take a moment to appreciate the incredible diversity of plants that call this challenging environment home. Even if you never spot a sentry milkvetch on its clifftop perch, knowing it’s out there, quietly doing its part to keep desert ecosystems running, makes the whole landscape a little more magical.

Sentry 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 cremnophylax Barneby - sentry milkvetch

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