North America Native Plant

Hawai’i Seagrass

Botanical name: Halophila hawaiiana

USDA symbol: HAHA3

Life cycle: perennial

Habit: forb

Native status: Native to Hawaii âš˜ Native to Pacific Basin excluding Hawaii  

Synonyms: Halophila ovalis (R. Br.) Hook. f. ssp. hawaiiana (Doty & B.C. Stone) Hartog (HAOVH)   

Hawai’i Seagrass: A Rare Marine Treasure You Can’t Grow in Your Garden If you’ve stumbled upon the name Hawai’i seagrass (Halophila hawaiiana) while researching native Hawaiian plants, you might be wondering if this unique species could find a home in your garden. Well, here’s the thing – unless your backyard ...

Rare plant alert!

Region: Conservation status by state

Status: S2: 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) ⚘

Hawai’i Seagrass: A Rare Marine Treasure You Can’t Grow in Your Garden

If you’ve stumbled upon the name Hawai’i seagrass (Halophila hawaiiana) while researching native Hawaiian plants, you might be wondering if this unique species could find a home in your garden. Well, here’s the thing – unless your backyard happens to be the Pacific Ocean, this particular native beauty isn’t destined for your landscape beds!

What Exactly is Hawai’i Seagrass?

Hawai’i seagrass is a fascinating perennial marine plant that lives its entire life underwater in shallow coastal waters. Unlike the grasses in your lawn, this seagrass is actually a flowering plant that has adapted to life in saltwater environments. It’s classified as a forb, meaning it’s a non-woody vascular plant – but one that has made the remarkable evolutionary leap to thrive beneath the waves.

This delicate species was once known by the synonym Halophila ovalis ssp. hawaiiana, but now stands proudly on its own as a distinct species endemic to Pacific waters.

Where Does Hawai’i Seagrass Call Home?

This marine native has a limited range, naturally occurring in the waters around Hawaii, Guam, and other U.S. Minor Outlying Islands in the Pacific. It’s truly a child of the Pacific, adapted specifically to the unique conditions of these tropical marine environments.

A Plant in Peril

Here’s where things get serious: Hawai’i seagrass carries a Global Conservation Status of S2, which means it’s imperiled due to extreme rarity. With typically only 6 to 20 known occurrences and few remaining individuals, this species is fighting for survival in our changing oceans.

This rarity status means that even if you could somehow recreate the perfect marine conditions (spoiler alert: you can’t in a typical garden setting), harvesting or disturbing wild populations would be both ecologically harmful and likely illegal.

Why This Marine Marvel Isn’t Garden-Friendly

Hawai’i seagrass is classified as an Obligate Wetland species – and not just any wetland, but specifically marine environments. This underwater specialist requires:

  • Constant saltwater immersion
  • Specific water temperatures and salinity levels
  • Sandy or muddy marine substrates
  • Precise light conditions filtered through seawater
  • Natural ocean currents and tidal movements

These requirements make it virtually impossible to cultivate in terrestrial gardens, freshwater ponds, or even most marine aquarium setups.

The Ecological Importance You’re Supporting from Afar

While you can’t plant Hawai’i seagrass in your backyard, understanding its importance helps you appreciate the incredible diversity of native Hawaiian ecosystems. Seagrass beds like those formed by this species serve as crucial nursery habitats for marine life, help prevent coastal erosion, and contribute to the overall health of coral reef ecosystems.

What Can You Do Instead?

If you’re passionate about supporting Hawaiian native plants, focus your gardening efforts on terrestrial natives that you can successfully grow and enjoy. Consider these alternatives that capture the spirit of Hawaiian flora:

  • Native Hawaiian grasses for coastal gardens
  • Indigenous flowering plants that support local pollinators
  • Coastal shrubs adapted to salt spray and sandy soils

You can also support seagrass conservation by choosing sustainable seafood, reducing coastal pollution, and supporting marine conservation organizations working to protect these precious underwater meadows.

The Bottom Line

Hawai’i seagrass represents the amazing diversity of native Hawaiian ecosystems, but it’s definitely not headed to a garden center near you anytime soon. This rare marine specialist belongs in its natural ocean habitat, where conservationists and marine biologists work tirelessly to ensure its survival.

Sometimes the best way to appreciate a native plant is to admire it from afar and support its conservation in the wild – and that’s exactly the case with this remarkable underwater treasure.

Hawai’i Seagrass

Classification

Group

Monocot

Kingdom

Plantae - Plants

Subkingdom

Tracheobionta - Vascular plants

Superdivision

Spermatophyta - Seed plants

Division

Magnoliophyta - Flowering plants

Subdivision
Class

Liliopsida - Monocotyledons

Subclass

Alismatidae

Order

Hydrocharitales

Family

Hydrocharitaceae Juss. - Tape-grass family

Genus

Halophila Thouars - seagrass

Species

Halophila hawaiiana Doty & B.C. Stone - Hawai'i seagrass

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