North America Native Plant

Bryan’s Flatsedge

Botanical name: Cyperus pennatiformis var. bryanii

USDA symbol: CYPEB

Life cycle: perennial

Habit: grass

Native status: Native to Hawaii  

Synonyms: Mariscus pennatiformis (Kük.) T. Koyama ssp. bryanii (MAPEB)   

Bryan’s Flatsedge: A Critically Rare Hawaiian Treasure Meet Bryan’s flatsedge (Cyperus pennatiformis var. bryanii), one of Hawaii’s most endangered native sedges. This perennial grass-like plant represents the kind of botanical treasure that makes Hawaii’s native flora so special—and so vulnerable. What Makes Bryan’s Flatsedge Special? Bryan’s flatsedge belongs to the ...

Rare plant alert!

Region: Conservation status by state

Status: S1T1: 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) ⚘

Bryan’s Flatsedge: A Critically Rare Hawaiian Treasure

Meet Bryan’s flatsedge (Cyperus pennatiformis var. bryanii), one of Hawaii’s most endangered native sedges. This perennial grass-like plant represents the kind of botanical treasure that makes Hawaii’s native flora so special—and so vulnerable.

What Makes Bryan’s Flatsedge Special?

Bryan’s flatsedge belongs to the sedge family (Cyperaceae), those grass-like plants that often get mistaken for actual grasses but have their own unique charm. As a Hawaiian endemic, this plant evolved in isolation over thousands of years, developing characteristics found nowhere else on Earth.

The plant is also known scientifically by the synonym Mariscus pennatiformis ssp. bryanii, reflecting some of the taxonomic shuffling that happens as botanists better understand plant relationships.

Where Does It Grow?

Bryan’s flatsedge is native exclusively to Hawaii, making it a true island endemic. However, its exact distribution within the Hawaiian islands is extremely limited.

A Conservation Concern

Here’s where things get serious: Bryan’s flatsedge has a Global Conservation Status of S1T1, which indicates it’s critically imperiled. This means the plant is at extremely high risk of extinction, with very few populations remaining in the wild.

For gardeners, this rarity status comes with important responsibilities. While we’d love to celebrate every native plant as a garden-worthy addition, Bryan’s flatsedge is so rare that it’s not something most gardeners should attempt to grow.

Should You Plant Bryan’s Flatsedge?

The short answer is: probably not, unless you’re working with a conservation organization or botanical institution. Here’s why:

  • The plant’s critical conservation status means wild populations need protection
  • Seeds or plants should only come from responsible conservation sources
  • Growing conditions and care requirements aren’t well-documented for home gardeners
  • Inadvertent hybridization with other sedges could threaten genetic integrity

What Can You Do Instead?

If you’re passionate about supporting Hawaiian native plants, consider these alternatives:

  • Support local conservation organizations working to protect rare Hawaiian plants
  • Plant other Hawaiian native sedges that are less threatened
  • Create habitat gardens using common Hawaiian native plants
  • Volunteer with botanical gardens or nature preserves

The Bigger Picture

Bryan’s flatsedge represents the fragility of island ecosystems and the importance of conservation efforts. While we can’t recommend growing this particular rarity in home gardens, its existence reminds us why protecting native plant habitats matters so much.

Every native plant garden—even one filled with more common species—contributes to the broader conservation story. By choosing native plants that are readily available and well-suited to cultivation, gardeners can support biodiversity while leaving the rarest species to the experts working on their recovery.

Sometimes the best way to love a plant is to appreciate it from afar and support the people working to ensure it survives for future generations.

Bryan’s Flatsedge

Classification

Group

Monocot

Kingdom

Plantae - Plants

Subkingdom

Tracheobionta - Vascular plants

Superdivision

Spermatophyta - Seed plants

Division

Magnoliophyta - Flowering plants

Subdivision
Class

Liliopsida - Monocotyledons

Subclass

Commelinidae

Order

Cyperales

Family

Cyperaceae Juss. - Sedge family

Genus

Cyperus L. - flatsedge

Species

Cyperus pennatiformis Kük. - coastal flatsedge

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