North America Native Plant

Oahu Flatsedge

Botanical name: Cyperus hypochlorus var. brevior

USDA symbol: CYHYB

Life cycle: perennial

Habit: grass

Native status: Native to Hawaii  

Synonyms: Mariscus hypochlorus (Hillebr.) C.B. Clarke ssp. brevior (Kük.) T. Koyama (MAHYB)   

Oahu Flatsedge: A Rare Hawaiian Native Worth Protecting Meet the Oahu flatsedge (Cyperus hypochlorus var. brevior), a special little sedge that calls Hawaii home. This isn’t your garden-variety ornamental grass – it’s a rare native plant that deserves our respect and protection rather than a spot in our backyard gardens. ...

Rare plant alert!

Region: Conservation status by state

Status: S3T3: Status is uncertain but is somewhere between the following rankings: 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 ⚘ 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. ⚘

Oahu Flatsedge: A Rare Hawaiian Native Worth Protecting

Meet the Oahu flatsedge (Cyperus hypochlorus var. brevior), a special little sedge that calls Hawaii home. This isn’t your garden-variety ornamental grass – it’s a rare native plant that deserves our respect and protection rather than a spot in our backyard gardens.

What Exactly Is Oahu Flatsedge?

Oahu flatsedge belongs to the sedge family (Cyperaceae), making it a grass-like perennial that’s actually more closely related to rushes than true grasses. Think of sedges as the understated cousins of the grass world – they’re often overlooked but play crucial roles in their ecosystems. This particular variety is scientifically known as Cyperus hypochlorus var. brevior, and it has a synonym that’s quite a mouthful: Mariscus hypochlorus ssp. brevior.

Where Does It Call Home?

As its common name suggests, this sedge is native to Hawaii, specifically found on Oahu. It’s what we call an endemic species – meaning it evolved right there in the Hawaiian Islands and exists nowhere else on Earth naturally. This makes it incredibly special from a conservation standpoint, as Hawaii is its one and only true home.

Why You Probably Shouldn’t Plant It (But Should Care About It)

Here’s where things get serious: Oahu flatsedge has a Global Conservation Status of S3T3, which indicates it’s rare and potentially vulnerable. When a plant is this uncommon, the best thing most of us can do is admire it from afar and support conservation efforts rather than trying to grow it ourselves.

If you’re absolutely determined to grow this sedge, please ensure any plant material comes from responsible, ethical sources that support conservation efforts rather than wild collection. Better yet, consider supporting local Hawaiian conservation organizations working to protect this species in its natural habitat.

Better Alternatives for Your Garden

Instead of seeking out this rare gem, why not explore other native sedges that are more readily available and appropriate for cultivation? If you’re outside of Hawaii, look for sedges native to your own region – they’ll be better adapted to your local conditions and won’t put pressure on rare species.

For Hawaiian gardeners, consider working with local native plant societies to find appropriate alternatives that can give you that sedge aesthetic while supporting local ecosystems without impacting rare species.

The Bigger Picture

Sometimes the most responsible thing we can do as plant lovers is to appreciate rare species like Oahu flatsedge without adding them to our wish lists. These plants remind us that not everything needs to be cultivated to be valued. By respecting their rarity and supporting their conservation, we’re helping ensure that future generations will be able to marvel at Hawaii’s unique botanical heritage.

Remember, the best gardens are those that work with nature, not against it – and sometimes that means leaving the rarest treasures right where they belong.

Oahu 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 hypochlorus Hillebr. - Oahu flatsedge

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