North America Native Plant

Coldwater Fumewort

Botanical name: Corydalis caseana aquaegelidae

USDA symbol: COCAA

Life cycle: perennial

Habit: forb

Native status: Native to the lower 48 states  

Synonyms: Corydalis aquae-gelidae M. Peck & Wilson (COAQ)   

Coldwater Fumewort: A Rare Pacific Northwest Native Worth Knowing If you’ve never heard of coldwater fumewort (Corydalis caseana aquaegelidae), you’re not alone. This elusive native plant is one of the Pacific Northwest’s best-kept botanical secrets, and for good reason – it’s quite rare and not something you’ll stumble across at ...

Rare plant alert!

Region: Conservation status by state

Status: S5T3: 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. ⚘ 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. ⚘

Coldwater Fumewort: A Rare Pacific Northwest Native Worth Knowing

If you’ve never heard of coldwater fumewort (Corydalis caseana aquaegelidae), you’re not alone. This elusive native plant is one of the Pacific Northwest’s best-kept botanical secrets, and for good reason – it’s quite rare and not something you’ll stumble across at your local nursery.

What Makes Coldwater Fumewort Special

Coldwater fumewort is a perennial forb, which simply means it’s a soft-stemmed herbaceous plant that comes back year after year. Unlike woody shrubs or trees, this delicate native lacks significant woody tissue and dies back to ground level during dormant seasons, regenerating from buds at or below the soil surface.

You might occasionally see this plant listed under its synonym, Corydalis aquae-gelidae, but both names refer to the same fascinating species that calls the Pacific Northwest home.

Where You’ll Find This Native Gem

This rare native is found exclusively in Oregon and Washington, making it a true regional treasure. Its limited geographic range contributes to its rarity and makes it a special addition for Pacific Northwest native plant enthusiasts.

A Word of Caution: Rarity Matters

Here’s where things get important: coldwater fumewort has a Global Conservation Status of S5T3, indicating it’s quite rare. If you’re fortunate enough to find this plant available, it’s crucial to ensure you’re purchasing from reputable sources that propagate plants responsibly rather than wild-collecting them.

Key points about growing rare natives:

  • Only purchase from nurseries that propagate their own plants
  • Never collect plants from wild populations
  • Consider this plant a conservation priority in your garden
  • Share seeds or divisions with other native plant enthusiasts when possible

Growing Coldwater Fumewort: What We Know

Unfortunately, detailed growing information for this specific subspecies is quite limited. However, as a member of the Corydalis family, we can make some educated guesses about its preferences based on its Pacific Northwest origins and its evocative common name.

The coldwater part of its name suggests this plant likely thrives in cool, moist conditions typical of the region’s mountain streams and shaded forest areas. As with many Pacific Northwest natives, it probably appreciates:

  • Cool, moist soil conditions
  • Partial to full shade
  • Good drainage despite moisture needs
  • Protection from hot afternoon sun

Should You Grow Coldwater Fumewort?

The honest answer is: probably only if you’re a serious native plant collector or conservationist. The rarity of this plant means it’s not readily available, and when it is found, it should be treated as a precious conservation specimen rather than just another garden plant.

If you’re interested in Corydalis species for your Pacific Northwest garden, consider looking into other native or regionally appropriate fumeworts that might be more readily available and better documented in terms of care requirements.

The Bottom Line

Coldwater fumewort represents one of those fascinating native plants that reminds us how much botanical diversity exists right in our own backyards. While it may not be the easiest native to grow or find, knowing about plants like this helps us appreciate the incredible variety of species that call the Pacific Northwest home.

If you do encounter this rare beauty, consider yourself lucky – and remember that with rarity comes responsibility. Every rare native plant in cultivation is a small victory for conservation and biodiversity.

Coldwater Fumewort

Classification

Group

Dicot

Kingdom

Plantae - Plants

Subkingdom

Tracheobionta - Vascular plants

Superdivision

Spermatophyta - Seed plants

Division

Magnoliophyta - Flowering plants

Subdivision
Class

Magnoliopsida - Dicotyledons

Subclass

Magnoliidae

Order

Papaverales

Family

Fumariaceae Marquis - Fumitory family

Genus

Corydalis DC. - fumewort

Species

Corydalis caseana A. Gray - Sierra fumewort

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