North America Native Plant

Howell’s Thelypody

Botanical name: Thelypodium howellii howellii

USDA symbol: THHOH

Life cycle: biennial

Habit: forb

Native status: Native to the lower 48 states  

Howell’s Thelypody: A Rare Pacific Northwest Native Worth Protecting If you’re passionate about native plant conservation and have a green thumb for rare species, you might be intrigued by Howell’s thelypody (Thelypodium howellii howellii). This little-known Pacific Northwest native is more than just another wildflower—it’s a botanical treasure that deserves ...

Rare plant alert!

Region: Conservation status by state

Status: S2T2: Status is uncertain but is somewhere between the following rankings: 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) ⚘ 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) ⚘

Howell’s Thelypody: A Rare Pacific Northwest Native Worth Protecting

If you’re passionate about native plant conservation and have a green thumb for rare species, you might be intrigued by Howell’s thelypody (Thelypodium howellii howellii). This little-known Pacific Northwest native is more than just another wildflower—it’s a botanical treasure that deserves our attention and protection.

What Makes Howell’s Thelypody Special?

Howell’s thelypody is a native forb that calls the Pacific Northwest home. As a herbaceous plant without woody stems, it fits into that wonderful category of wildflowers that return year after year, living as either a biennial or perennial depending on conditions. What makes this plant truly special, however, is its rarity—it carries a Global Conservation Status of S2T2, meaning it’s considered very rare and vulnerable.

Where Does It Grow?

This native beauty has a limited range, naturally occurring in just three states: California, Oregon, and Washington. Its restricted distribution is part of what makes it so precious to conservationists and native plant enthusiasts alike.

Should You Grow Howell’s Thelypody?

Here’s where we need to have an important conversation about responsible gardening. While Howell’s thelypody is undoubtedly a fascinating native plant, its rare status means we need to approach it with extra care and consideration.

The Conservation Consideration

Given its S2T2 conservation status, this plant should only be grown using responsibly sourced material—never collected from the wild. If you’re considering adding this rare gem to your garden, here are some important guidelines:

  • Only purchase from reputable native plant nurseries that can verify their propagation methods
  • Ensure any seeds or plants come from legitimate conservation programs
  • Never collect seeds or plants from wild populations
  • Consider participating in or supporting conservation efforts for this species

Garden Role and Landscape Use

Due to its rarity and specialized nature, Howell’s thelypody isn’t your typical garden center find. It’s best suited for:

  • Specialized native plant gardens focused on conservation
  • Botanical collections with rare Pacific Northwest species
  • Educational gardens that showcase regional biodiversity
  • Conservation-focused landscape projects

Growing Conditions and Care

While specific growing requirements for Howell’s thelypody aren’t well-documented (another sign of how rare it is!), we can make some educated assumptions based on its native habitat in the Pacific Northwest. It likely prefers:

  • Well-draining soils typical of its native range
  • Conditions similar to other Pacific Northwest natives
  • Protection from extreme weather conditions
  • Minimal disturbance once established

Wildlife and Pollinator Benefits

As a native forb, Howell’s thelypody likely provides some benefits to local wildlife and pollinators, though specific relationships haven’t been well-studied. Native plants typically support native insects and other wildlife in ways that non-native species simply cannot match.

The Bottom Line

Howell’s thelypody represents something special in the world of native plants—a rare species that connects us to the unique biodiversity of the Pacific Northwest. While most gardeners should probably focus on more common native alternatives, those with experience in rare plant cultivation and access to responsibly sourced material might consider this plant as part of conservation efforts.

If you’re interested in supporting Pacific Northwest native plants but want more readily available options, consider looking into other native forbs from the region that can provide similar ecological benefits without the conservation concerns.

Remember, every rare plant species we help protect today is a gift we’re giving to future generations of both gardeners and the wildlife that depends on these unique native ecosystems.

Howell’s Thelypody

Classification

Group

Dicot

Kingdom

Plantae - Plants

Subkingdom

Tracheobionta - Vascular plants

Superdivision

Spermatophyta - Seed plants

Division

Magnoliophyta - Flowering plants

Subdivision
Class

Magnoliopsida - Dicotyledons

Subclass

Dilleniidae

Order

Capparales

Family

Brassicaceae Burnett - Mustard family

Genus

Thelypodium Endl. - thelypody

Species

Thelypodium howellii S. Watson - Howell's thelypody

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