Crinum thaianum (Thai onion plant)

Crinum thaianum (Thai onion plant, Water onion, Onion plant) is an endangered species of flowering plant of the family amaryllidaceae, endemic to the coastal plain of southern Thailand in Ranong and Phang Nga Provinces. Its natural habitat occurs along the banks of running streams where the roots and bulbs are submerged but the flowering stalks holding the umbel of large, showy, white flowers are above the water's surface. The species is threatened due to habitat destruction caused by dredging of rivers and streams for removal of sediments and rock for construction and land reclamation purposes; and also by diversion of the rivers and streams for agricultural purposes.

Crinum thaianum is a geophytic plant cultivated as an aquatic ornamental plant to decorate aquaria. Mature bulbs are up to 7 cm in diameter and about 15 cm high. It has elongated, tough, ribbon-like, bright green leaves, up to 2 m long that grow from a bulb that look like an onion. The leaves float in the direction of the current, or piled in loops in stiller waters. The leaves are tough but snap easily, and are usually not more than 10 leaves per bulb. The inflorescence is an umbel holding 5-8 showy, white flowers on a long flower stalk above the water's surface. Flowering occurs mainly during the monsoon season, from August to October.

Crinum thaianum is an easy bulb that grows in most conditions. Plant so the top 2/3 of the bulb is visible, otherwise the bulb tends to rot. The roots grow fairly quickly, but has a long acclimation period before new leaves start to grow, normally in a couple of weeks.

Crinum thaianum grows in clear running fresh water, usually in wide and open streams and rivers a few centimeters to two meters in depth, depending on the seasonal water level. The soil is usually mixed gravel or sandy loam.

Propagation is by vegetative reproduction of daughter plants or bulblets.

Crinum thaianumCrinum thaianum
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authorshipIto Y, Barfod A
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