North America Native Plant

Cascara Serpentine Buckthorn

Botanical name: Frangula purshiana ultramafica

USDA symbol: FRPUU

Life cycle: perennial

Habit: shrub

Native status: Native to the lower 48 states  

Cascara Serpentine Buckthorn: A Rare California Native Worth Knowing If you’re drawn to unique native plants with interesting stories, you might want to learn about Cascara serpentine buckthorn (Frangula purshiana ultramafica). This perennial shrub represents one of those fascinating plants that reminds us how much we still have to discover ...

Rare plant alert!

Region: Conservation status by state

Status: S4S5T2: Status is uncertain but is somewhere between the following rankings: Subspecies or variety is 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) ⚘ 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 ⚘ 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. ⚘

Cascara Serpentine Buckthorn: A Rare California Native Worth Knowing

If you’re drawn to unique native plants with interesting stories, you might want to learn about Cascara serpentine buckthorn (Frangula purshiana ultramafica). This perennial shrub represents one of those fascinating plants that reminds us how much we still have to discover about our native flora.

What Makes This Plant Special

Cascara serpentine buckthorn is a multi-stemmed woody shrub that typically grows less than 13-16 feet tall. Like many shrubs, it usually develops several stems from or near the ground, though environmental conditions can sometimes encourage different growth patterns. What makes this particular plant noteworthy is its apparent connection to California’s unique serpentine soils – those mineral-rich, challenging growing conditions that have given rise to some truly specialized plant communities.

Where You’ll Find It (Or Won’t)

This native species calls California home, where it has adapted to specific environmental conditions. Its distribution appears to be quite limited within the state, which brings us to an important consideration for any gardener interested in this plant.

A Word About Rarity

Here’s something crucial to know: Cascara serpentine buckthorn has a conservation status that suggests it’s not your everyday garden center find. With limited populations and specialized habitat requirements, this plant falls into a category where responsible gardening practices become especially important.

If you’re considering this plant for your garden: Only source it from reputable native plant nurseries that can verify responsible propagation methods. Never collect plants or seeds from wild populations – this can harm already limited natural communities.

Growing Challenges and Considerations

Honestly, we’re still learning about the specific growing requirements for this particular plant. What we do know suggests it’s probably not the easiest shrub to establish in typical garden conditions. Plants adapted to serpentine soils often have very specific mineral and drainage requirements that can be tricky to replicate.

The Bigger Picture

While Cascara serpentine buckthorn might not be the right choice for every garden (or even most gardens), it represents something valuable in our native plant communities. Plants like this often:

  • Support specialized wildlife communities
  • Help maintain unique ecosystem functions
  • Preserve genetic diversity within plant families
  • Offer insights into plant adaptation and evolution

Alternative Considerations

If you’re drawn to the idea of supporting California’s native Cascara family, consider looking into the more widely available Frangula purshiana (standard Cascara buckthorn) or Frangula californica (California buckthorn). These related species can often provide similar ecological benefits while being more suitable for home gardens.

The Bottom Line

Cascara serpentine buckthorn reminds us that native gardening isn’t just about what we can grow – it’s also about understanding and respecting the plants that belong in wild spaces. While this particular species might not be destined for your backyard, knowing about it helps us appreciate the incredible diversity of California’s native flora.

If you’re passionate about rare natives and have experience with challenging plants, this might be worth exploring through specialized native plant societies or botanical gardens. Just remember: rare plants require rare responsibility.

Cascara Serpentine Buckthorn

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

Rhamnales

Family

Rhamnaceae Juss. - Buckthorn family

Genus

Frangula Mill. - buckthorn

Species

Frangula purshiana (DC.) A. Gray - Cascara buckthorn

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