Water Onion Plant Care
Crinum thaianum J.Schulze
Updated · Sources · How we source care data
Crinum thaianum, also called the Thai onion plant or water onion, or Phlap Phueng Than, is an emergent plant species, endemic to the coastal plain of Ranong and Phang Nga Provinces, Thailand. Its natural habitat is to grow along the banks of flowing, medium- to fast-running streams, where its roots and bulb are submerged in the sediment, while its leaves grow long in the current and can access fresh air at the surface.
Every 7–10 days
Full sun to partial shade
60–80°F
40–70%
At a glance
How do you care for Water Onion?
Water Water Onion every 7–10 days, letting the top layer of soil dry out between waterings, and give it full sun to partial shade. It prefers temperatures of 60–80°F (16–27°C) and 40–70% humidity. Fertilize it every 6 months during the growing season. It is reported as toxic to pets, so keep it out of reach of pets.
Where Is the Water Onion Native To?
What Is the Water Onion?
Water Onion (Crinum thaianum) belongs to the Amaryllidaceae family within the Crinum genus. Water Onion is native to the coastal plain of Ranong and Phang Nga Provinces, Thailand. Water Onion is also known as Thai Crinum.
Water Onion displays a tall, clumping perennial growth habit, reaching up to 3 ft tall with a spread of approximately 2 ft. Water Onion produces fragrant, trumpet-shaped flowers in shades of white, pink, or red.
Leaf size: approximately 18 inches.
How Often Should You Water a Water Onion?
Crinum thaianum requires watering every 7–10 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 7–10 days
Let soil partially dry between waterings
What Light Does the Water Onion Need?
Water Onion thrives in full sun to partial shade.
Light Requirement
Full sun to partial shade
What Temperature and Humidity Does the Water Onion Prefer?
Crinum thaianum grows best at temperatures of 60–80°F. Water Onion prefers humidity levels of 40–70%.
Temperature
60–80°F
Humidity
40–70%
What Soil Mix Works Best for a Water Onion?
Rich, well-draining soil with added compost for nutrients. Good drainage is essential for Water Onion to prevent waterlogging, which leads to root rot and fungal issues.
How Often Should You Fertilize a Water Onion?
Feed Water Onion every 6 months 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 6 months
During the growing season
The PlantoScan app can remind you when to water and when to fertilize each plant.
How Do You Repot a Water Onion?
Repot every 2-3 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 Water Onion?
Water Onion can be propagated through offsets, division of bulbs. Similar propagation techniques also apply to macowan's crinum lily plant care, which shares the same genus.
Is the Water Onion Toxic to Pets and Children?
Toxic (caution)
Reported as toxic in our plant data. Not verified by the ASPCA.
Toxic to humans and pets if ingested
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 Water Onion?
Water Onion is susceptible to aphids, spider mites, thrips. 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 Water Onion Need?
Water Onion grows outdoors in USDA Zone 13a. It survives winters down to planting zone 13a. Water Onion is native to the coastal plain of Ranong and Phang Nga Provinces, Thailand. In cooler regions, grow Water Onion as a houseplant or bring it indoors before the first frost.
Hardiness Zone
Zone 13a
Keep exploring plants
Water Onion 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 Crinum genus — compare its care with other Crinum species on PlantoScan.
Crinum is part of the Amaryllidaceae plant family — browse all Amaryllidaceae genera and species.
Water Onion thrives in bright light and direct sun — see other bright-light plants.
More Crinum Species
Other Crinum species in PlantoScan's care catalogue share similar watering, light, and soil preferences:
Sources
- Scientific name & taxonomy: Crinum thaianum J.Schulze, family Amaryllidaceae (first published in Pl. Life 27: 127 (1971)) — World Flora Online record, IPNI name record.
- Pet toxicity: Water Onion is reported as toxic to pets in our plant data (not verified by the ASPCA), so treat it with caution. Checked against the ASPCA plant list; any other toxicity note on this page comes from PlantoScan's plant database.
- Hardiness zone: USDA Zone 13a, calculated from the plant's minimum temperature.
- 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.
Identify Plants Like the
Water Onion Instantly
Scan any plant with your phone camera and get instant ID, care tips, water and fertilizer reminders, and health checks — all in one app.
Free
to download
iOS & Android
platforms
Light & dark
mode
100,000+
species