Photo: Thomas IrvineCC BY 4.0via iNaturalistresized / cropped
Hawaiian seagrass Plant Care
Halophila hawaiiana Doty & B.C.Stone
Updated · Sources · How we source care data
Halophila hawaiiana, also known as the Hawaiian seagrass, is a distinctive plant with long, narrow leaves that are bright green in color. This seagrass is native to the clear waters of Hawaii and is popular among plant enthusiasts for its unique appearance and important role in marine ecosystems.
Every 7–14 days
Full sun to partial shade
70–85°F
60–80%
At a glance
How do you care for Hawaiian seagrass?
Water Hawaiian seagrass every 7–14 days, letting the top layer of soil dry out between waterings, and give it full sun to partial shade. It prefers temperatures of 70–85°F (21–29°C) and 60–80% humidity. Fertilize it every month during the growing season.
What Is the Hawaiian seagrass?
Hawaiian seagrass (Halophila hawaiiana) belongs to the Hydrocharitaceae family within the Halophila genus. Hawaiian seagrass is native to Hawaiiheight: 0.5width: 0.25fertilizer: 1wateringMin: 7wateringMax: 14humidityMin: 60humidityMax: 80temperatureMin: 70temperatureMax: 85leafSize: 6.
Hawaiian seagrass displays a spreading aquatic perennial growth habit, reaching up to tall with a spread of approximately . Hawaiian seagrass produces small inconspicuous flowers underwater.
Leaf size: approximately 6 inches.
How Often Should You Water a Hawaiian seagrass?
Halophila hawaiiana requires watering every 7–14 days. Allow the top layer of soil to dry between waterings to prevent root rot. Reduce watering frequency during winter when growth slows.
Watering Frequency
Every 7–14 days
Let soil partially dry between waterings
What Light Does the Hawaiian seagrass Need?
Hawaiian seagrass thrives in full sun to partial shade.
Light Requirement
Full sun to partial shade
What Temperature and Humidity Does the Hawaiian seagrass Prefer?
Halophila hawaiiana grows best at temperatures of 70–85°F. Hawaiian seagrass prefers humidity levels of 60–80%. A pebble tray or humidifier helps maintain adequate moisture around the plant.
Temperature
70–85°F
Humidity
60–80%
What Soil Mix Works Best for a Hawaiian seagrass?
Sandy, well-draining aquatic substrate with high organic content. Good drainage is essential for Hawaiian seagrass to prevent waterlogging, which leads to root rot and fungal issues.
How Often Should You Fertilize a Hawaiian seagrass?
Feed Hawaiian seagrass every month during the growing season (spring and summer) with a balanced fertilizer diluted to the strength on the label.
Pause feeding in autumn and winter, when growth slows, and never fertilize dry soil — water first.
Fertilizing
Every month
During the growing season
The PlantoScan app can remind you when to water and when to fertilize each plant.
How Do You Repot a Hawaiian seagrass?
Repot every 1-2 years in early spring. Choose a pot one size larger than the current container, and ensure it has drainage holes to allow excess water to escape.
How Do You Propagate a Hawaiian seagrass?
Hawaiian seagrass can be propagated through vegetative propagation, division, rhizome cuttings. Similar propagation techniques also apply to heart-shaped seagrass plant care, which shares the same genus.
Is the Hawaiian seagrass Toxic to Pets and Children?
Pet safety not verified
The ASPCA does not list Hawaiian seagrass, so we can't confirm whether it is safe for cats and dogs. Keep pets from chewing it as a precaution.
This is a general caution, not veterinary or medical advice. If your pet ate a plant, contact your vet or animal poison control.
See all plants toxic to cats and plants toxic to dogs.
What Pests and Diseases Affect the Hawaiian seagrass?
Hawaiian seagrass is susceptible to algae, aquatic weeds. Inspect the foliage regularly, especially along leaf undersides and stems. Treat infestations promptly with insecticidal soap or neem oil to prevent spread.
Yellow leaves, brown tips or drooping? See common plant problems and how to fix them.
What USDA Hardiness Zone Does the Hawaiian seagrass Need?
Hawaiian seagrass grows outdoors in USDA Zone 11a – 12b. It survives winters down to planting zone 11a. Hawaiian seagrass is native to Hawaiiheight: 0.5width: 0.25fertilizer: 1wateringMin: 7wateringMax: 14humidityMin: 60humidityMax: 80temperatureMin: 70temperatureMax: 85leafSize: 6. In cooler regions, grow Hawaiian seagrass as a houseplant or bring it indoors before the first frost.
Hardiness Zone
Zone 11a – 12b
Keep exploring plants
Hawaiian seagrass is one of many species covered in the complete plant care and identification guide, which groups plants by genus, attribute, and popularity.
It belongs to the Halophila genus — compare its care with other Halophila species on PlantoScan.
Halophila is part of the Hydrocharitaceae plant family — browse all Hydrocharitaceae genera and species.
Hawaiian seagrass thrives in bright light and direct sun — see other bright-light plants.
More Halophila Species
Other Halophila species in PlantoScan's care catalogue share similar watering, light, and soil preferences:
Sources
- Scientific name & taxonomy: Halophila hawaiiana Doty & B.C.Stone, family Hydrocharitaceae (first published in Brittonia 18: 303 (1967)) — World Flora Online record, IPNI name record.
- Pet toxicity: Pet safety not verified: the ASPCA does not list Hawaiian seagrass, so we can't confirm whether it is safe for cats and dogs. Checked against the ASPCA plant list; any other toxicity note on this page comes from PlantoScan's plant database.
- Photo: Thomas Irvine, CC BY 4.0, iNaturalist — original.
- Hardiness zone: USDA Zone 11a – 12b, estimated from the plant's typical growing conditions.
- Care values(watering, light, temperature, humidity, soil, fertilizing): PlantoScan's plant database, filtered by automatic plausibility checks — values that fail them are hidden. How we source and check plant data.
Spotted a mistake? Email info@upvision.media with the page link — we check and correct reported errors.
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