North America Native Plant

Flat-top Broomrape

Botanical name: Orobanche corymbosa mutabilis

USDA symbol: ORCOM

Life cycle: annual

Habit: forb

Native status: Native to Canada âš˜ Native to the lower 48 states  

Flat-Top Broomrape: A Rare Parasitic Wildflower of the Pacific Northwest Meet the flat-top broomrape (Orobanche corymbosa mutabilis), one of nature’s most unusual native plants. This quirky annual belongs to a fascinating group of parasitic plants that have ditched the whole make your own food approach in favor of freeloading off ...

Rare plant alert!

Region: Conservation status by state

Status: S4T3?: Status is uncertain but is somewhere between the following rankings: Inexact rank: ⚘ 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. ⚘ 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 ⚘

Flat-Top Broomrape: A Rare Parasitic Wildflower of the Pacific Northwest

Meet the flat-top broomrape (Orobanche corymbosa mutabilis), one of nature’s most unusual native plants. This quirky annual belongs to a fascinating group of parasitic plants that have ditched the whole make your own food approach in favor of freeloading off other plants. While you won’t be adding this one to your garden beds anytime soon, it’s definitely worth understanding this remarkable native species.

What Makes Flat-Top Broomrape Special?

As a member of the broomrape family, this plant is what botanists call a holoparasite – meaning it depends entirely on other plants for survival. Unlike most plants that use chlorophyll to make their own food through photosynthesis, flat-top broomrape has essentially given up that independent lifestyle and taps into the root systems of host plants to steal their nutrients.

This annual forb lacks the woody tissue you’d find in shrubs and trees, instead growing as a herbaceous plant that completes its entire life cycle in a single growing season.

Where You’ll Find This Rare Native

Flat-top broomrape is native to both Canada and the United States, with its known distribution limited to British Columbia and Washington state. This makes it a true Pacific Northwest specialty – a regional native that’s adapted to the unique conditions of this corner of North America.

Why You Shouldn’t Try Growing It (And Why That’s Okay)

Here’s where we need to have a frank conversation: this isn’t a plant for your garden, and there are several good reasons why:

  • Rarity concerns: With a Global Conservation Status of S4T3?, this plant’s conservation status is somewhat uncertain, making it important to leave wild populations undisturbed
  • Parasitic nature: Since it requires specific host plants to survive, it can’t be grown like typical garden plants
  • Specialized requirements: Even if you wanted to try, the complex relationships between parasitic plants and their hosts make cultivation extremely challenging
  • Unknown growing conditions: Limited research means we don’t fully understand its specific habitat requirements

Appreciating Flat-Top Broomrape in Nature

Instead of trying to grow this unusual native, the best way to appreciate flat-top broomrape is to learn to identify it during hikes in its native Pacific Northwest range. Keep your eyes peeled in natural areas of British Columbia and Washington, where you might spot this rare parasitic plant doing its thing in the wild.

Since this is an annual plant, it completes its entire life cycle within one growing season, making timing important if you hope to spot it in bloom.

Supporting Native Plant Conservation

Rather than attempting to cultivate this rare parasitic species, consider supporting Pacific Northwest native plant conservation in other ways:

  • Plant other native species from the region in your garden
  • Support local native plant societies and conservation organizations
  • Participate in citizen science projects that help track rare plant populations
  • Practice Leave No Trace principles when enjoying natural areas where rare plants like flat-top broomrape might grow

The Bottom Line

Flat-top broomrape represents the fascinating diversity of native plant life in the Pacific Northwest. While it’s not destined for garden beds, this rare parasitic annual reminds us that native plants have evolved incredible strategies for survival – even if that means giving up photosynthesis and becoming nature’s ultimate freeloader. The best thing we can do for plants like this is to appreciate them in their natural habitats and support conservation efforts that protect the ecosystems where these botanical oddities thrive.

Flat-top Broomrape

Classification

Group

Dicot

Kingdom

Plantae - Plants

Subkingdom

Tracheobionta - Vascular plants

Superdivision

Spermatophyta - Seed plants

Division

Magnoliophyta - Flowering plants

Subdivision
Class

Magnoliopsida - Dicotyledons

Subclass

Asteridae

Order

Scrophulariales

Family

Orobanchaceae Vent. - Broom-rape family

Genus

Orobanche L. - broomrape

Species

Orobanche corymbosa (Rydb.) Ferris - flat-top broomrape

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