Crinum thaianum 

Scope: Global
Language: English

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Taxonomy [top]

Kingdom Phylum Class Order Family
Plantae Tracheophyta Liliopsida Asparagales Amaryllidaceae

Scientific Name: Crinum thaianum J.Schulze
Common Name(s):
English Onion Plant, Thai Water Onion, Water Onion

Assessment Information [top]

Red List Category & Criteria: Endangered B1ab(ii,iii,iv,v)+2ab(ii,iii,iv,v) ver 3.1
Year Published: 2011
Date Assessed: 2008-06-06
Assessor(s): Soonthornnawaphat, S., Bambaradeniya, C. & Sukpong, P.
Reviewer(s): Hilton-Taylor, C. & Lutz, M.L.
The Water Onion has a very restricted range in southern Thailand, with an extent of occurrence of about 641 km² and an area of occupancy of about 48 km². The population is severely fragmented by habitat loss (only 3-5% of the original habitat remains) and there has been rapid population declines in some areas as a result (70% decline in the Nakha River during the period 2003-2008), and there has been local extinction in some streams within its range. The threats to the habitats and the species (exploitation) are all ongoing, hence there is continuing decline in a number of parameters. The species is therefore listed as Endangered and it could well become Critically Endangered in the near future if these trends continue.

IUCN staff in the region are trying to raise awareness about this species and have also been promoting habitat restoration and reintroduction projects in an effort to conserve this species.

Geographic Range [top]

Range Description:Originally found on the coastal plain of southern Thailand (Leeratiwong and Jornead 2005), but is now confined to isolated patches on a few rivers and streams in Phang Nga and Ranong provinces. Phang Nga province: Khlong Khura Buri/ Nang Yon, Khlong Banglu, Khlong Tam Nung, Khlong Ban Krung, Khlong Bang Pao Moo and Ranong province: Khlong Nakha; Khlong Kapoe, Khlong Bangpong, Khlong Suan Mai, Khlong Ta Pud (; IUCN survey). Occurs at low elevations below 150 m.
Countries occurrence:
Additional data:
Estimated area of occupancy (AOO) - km2:48Continuing decline in area of occupancy (AOO):Yes
Estimated extent of occurrence (EOO) - km2:641
Continuing decline in number of locations:Yes
Lower elevation limit (metres):50
Upper elevation limit (metres):150
Range Map:Click here to open the map viewer and explore range.

Population [top]

Population:The population is very fragmented and declining.
Current Population Trend:Decreasing
Additional data:
Continuing decline of mature individuals:Yes
Population severely fragmented:Yes
Continuing decline in subpopulations:Yes

Habitat and Ecology [top]

Habitat and Ecology:This geophytic plant grows in clear running fresh water, usually in wide and open streams and rivers a few centimetres to two meters in depth depending on the seasonal water level. The soil is usually a sandy loam or mixed gravel. Some streams are shaded, however, in all their sites Crinum receive sunlight at least temporarily ( It prefers water temperatures of 22-30°C.

Mature bulbs reach 7 cm in diameter and about 15 cm high. The elongated (up to two metres long) float in the direction of the current, or in stiller water are piled in loops. Flowering occurs mainly during the monsoon season (August-October). The inflorescence comprises five to eight flowers. The plant also reproduces vegetatively through the production of bulblets.

The data on the phenology of water onion and water depth in Nakha river,  maintained by Mrs. Oy Onkhow (co-leader of a local community based organization – ‘Pleun Prai Sri Naka’ -  involved in conservation work in Ranong Province, highlights the following:

January (average water depth of 3-4 m): germination from seeds and leaf production from bulbs starts

February - July (average water depth starts at 1-2 m in March and increases to 5-6 m by July): leaf growth

August (average water depth 6-8 m): flowering is initiated

September (average water depth 8-9 m): peak flowering

October (average water depth 6-9 m): seed formation

November to December (average water depth drops from 6 m down to 4 m): seed is dispersed and laves die back

Preliminary observations on the mid areas of the Nakha River, by a team of IUCN scientists on the 3rd of June 2008 revealed the following: The speed of water flow in mid areas of Nakha River ranged from 0.25-3 m/s. The main population is restricted to a 600 m stretch (width – 30 m; depth 1-2.5 m), which has a muddy substrate. The growth was very dense towards the edge of the river. The water flow in this stretch was below 0.3 m/s. The area received ample sunlight. The length of the leaves ranged from 1-3 m, with each bulb having 20-40 leaves. Several fish were observed in this stretch, beneath the thick growth of this plant, which provided an ideal refuge to them. A thin layer of sediment was clearly visible on the leaf surface. Clumps of washed out Water Onion were observed on either side of the river bank, these had been removed by the fast flow of the water.     

The Water Onion is a very important aquatic plant that functions as a keystone species in its aquatic habitats. It provides important habitat for native freshwater fish species such as the Soro Brook Carp (Tor soro), which use it as a habitat to lay eggs.  Other aquatic species such as water snails and frogs also use it as breeding habitat. Other native fish eat the young leaves of Water Onion.
Continuing decline in area, extent and/or quality of habitat:Yes

Use and Trade [top]

Use and Trade: The species is popular with aquarists because it is easy to maintain, highly tolerant of temperature and light variations. The bulb is also used to produce a cream for softening the skin.

Investigations carried out  by IUCN revealed that a buyer in Kuraburi used to purchase about 10,000 bulbs/day from local communities about 10 years ago. However, this amount has declined sharply over the past four years. At present (2008), he purchases at the rate of 1 Baht per bulb, and sells it to an exporting company in Bangkok at 5 Baht/bulb. The export company sells each bulb for 2-5 US$, in foreign destinations.

Threats [top]

Major Threat(s):

A major threat to the habitat of this species is the dredging of rivers and streams for removal of sediment and rock for construction and land reclamation purposes (this has also increased the speed of water flow in habitats of the Water Onion, where entire subpopulations have been dislodged). Also threatened by diversion of the rivers and streams for agricultural purposes. There is also extensive changes in the ecology of the streams and rivers due to land use changes in the adjoining areas (e.g., clearing of forest for agriculture) and resultant land-based erosion and river bank erosion (the substrate of the Nakha and Kuraburi rivers has changed drastically over the past 10 years, due to erosion. The muddy substrate that facilitates the growth of Water Onion has been replaced by pebbles, rock and gravel, in large areas of these rivers. Collection of bulbs from the wild for sale to the international trade for home fish ponds and aquaria is also a threat which needs closer monitoring.

Conservation Actions [top]

Conservation Actions: The Office of National Environmental Policy and Planning in Thailand (ONEPP) has declared this species as nationally endangered ( Local conservation groups in the Ranong province have also initiated the conservation of this species in its wild habitats (Youth group and Plern Prai Sri Na Ca Conservation Group established by Klong Na Ca Wildlife Sanctuary). The youth group is involved in awareness campaigns, ex situ propagation of Water Onion in nurseries, rescue of dislodged Water Onion deposited on river banks and subsequent re-planting in the wild. The Pleun Prai Sri Na Kha Conservation Group, together with the local authority organizes tourist visits (in dinghy paddle boats) along Na Kha river to observe Crinum thaianum during its flowering period (October-December) every year. About 600 Thai tourists visited the area in 2007. A fee of 450 Thai Baht (ca. 15 US$) is charged to each visitor.

Classifications [top]

5. Wetlands (inland) -> 5.1. Wetlands (inland) - Permanent Rivers/Streams/Creeks (includes waterfalls)
suitability:Suitable  major importance:Yes
5. Wetlands (inland) -> 5.2. Wetlands (inland) - Seasonal/Intermittent/Irregular Rivers/Streams/Creeks
2. Land/water management -> 2.1. Site/area management
2. Land/water management -> 2.3. Habitat & natural process restoration
3. Species management -> 3.1. Species management -> 3.1.1. Harvest management
3. Species management -> 3.1. Species management -> 3.1.2. Trade management
3. Species management -> 3.3. Species re-introduction -> 3.3.1. Reintroduction
3. Species management -> 3.4. Ex-situ conservation -> 3.4.1. Captive breeding/artificial propagation
4. Education & awareness -> 4.2. Training
4. Education & awareness -> 4.3. Awareness & communications

In-Place Research, Monitoring and Planning
In-Place Land/Water Protection and Management
  Occur in at least one PA:Yes
In-Place Species Management
In-Place Education
11. Climate change & severe weather -> 11.4. Storms & flooding
♦ timing:Ongoing    
→ Stresses
  • 1. Ecosystem stresses -> 1.2. Ecosystem degradation
  • 2. Species Stresses -> 2.1. Species mortality
  • 2. Species Stresses -> 2.2. Species disturbance

2. Agriculture & aquaculture -> 2.1. Annual & perennial non-timber crops -> 2.1.3. Agro-industry farming
♦ timing:Ongoing    
→ Stresses
  • 1. Ecosystem stresses -> 1.1. Ecosystem conversion
  • 1. Ecosystem stresses -> 1.2. Ecosystem degradation

2. Agriculture & aquaculture -> 2.2. Wood & pulp plantations -> 2.2.1. Small-holder plantations
♦ timing:Ongoing    
→ Stresses
  • 1. Ecosystem stresses -> 1.1. Ecosystem conversion
  • 1. Ecosystem stresses -> 1.2. Ecosystem degradation

2. Agriculture & aquaculture -> 2.2. Wood & pulp plantations -> 2.2.2. Agro-industry plantations
♦ timing:Ongoing    
→ Stresses
  • 1. Ecosystem stresses -> 1.1. Ecosystem conversion
  • 1. Ecosystem stresses -> 1.2. Ecosystem degradation

3. Energy production & mining -> 3.2. Mining & quarrying
♦ timing:Ongoing    
→ Stresses
  • 1. Ecosystem stresses -> 1.1. Ecosystem conversion
  • 1. Ecosystem stresses -> 1.2. Ecosystem degradation

5. Biological resource use -> 5.2. Gathering terrestrial plants -> 5.2.1. Intentional use (species is the target)
♦ timing:Ongoing    
→ Stresses
  • 2. Species Stresses -> 2.1. Species mortality

7. Natural system modifications -> 7.2. Dams & water management/use -> 7.2.3. Abstraction of surface water (agricultural use)
♦ timing:Ongoing    
→ Stresses
  • 1. Ecosystem stresses -> 1.1. Ecosystem conversion
  • 1. Ecosystem stresses -> 1.2. Ecosystem degradation

7. Natural system modifications -> 7.2. Dams & water management/use -> 7.2.9. Small dams
♦ timing:Ongoing    
→ Stresses
  • 1. Ecosystem stresses -> 1.1. Ecosystem conversion
  • 1. Ecosystem stresses -> 1.2. Ecosystem degradation

9. Pollution -> 9.3. Agricultural & forestry effluents -> 9.3.2. Soil erosion, sedimentation
♦ timing:Ongoing    
→ Stresses
  • 1. Ecosystem stresses -> 1.1. Ecosystem conversion
  • 1. Ecosystem stresses -> 1.2. Ecosystem degradation

1. Research -> 1.2. Population size, distribution & trends
1. Research -> 1.5. Threats
3. Monitoring -> 3.1. Population trends
3. Monitoring -> 3.2. Harvest level trends
3. Monitoring -> 3.3. Trade trends
3. Monitoring -> 3.4. Habitat trends

♦  Medicine - human & veterinary
 Local : ✓   National : ✓ 

♦  Pets/display animals, horticulture
 International : ✓ 

♦  Establishing ex-situ production *

Bibliography [top]

IUCN. 2011. IUCN Red List of Threatened Species (ver. 2011.2). Available at: (Accessed: 10 November 2011).

Leeratiwong, C. and Jornead, S. 2005. Species diversity of vascular plants in Si Phang-nga National Park, Phangnga Province. J.Songklanakarin Journal of Science and Technology 27(4): 769-787.

Citation: Soonthornnawaphat, S., Bambaradeniya, C. & Sukpong, P. 2011. Crinum thaianum. The IUCN Red List of Threatened Species 2011: e.T201627A9154955. . Downloaded on 21 September 2018.
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