There have been many, varied views amongst botanistis on how to deliminate the various species in the genus Trapa, with interpretations ranging from almost 80 distinct species right down to the concept that there is only one, highly vaiable species. We are following the interpretation in Plants of the World online (see https://powo.science.kew.org/taxon/urn:lsid:ipni.org:names:28563-1, accessed 01/05/2024), which accepts 8 distinct species in the genus, including the highly variable Trapa natans which is itself divided into 8 varieties[].

Common Name:

General Information

Trapa incisa is an annual, aquatic plant with a rosette of floating leaves and a submerged stem; floating in shallow water by means of inflated petioles[].
The plant is harvested from the wild, and sometimes also cultivated, for its edible seeds[].
Trapa incisa is a common plant in China and southeast Asia and is not facing any specific threats. The plant is classified as 'Least Concern' in the IUCN Red List of Threatened Species(2013)[].

Known Hazards

We have no specific information for this species, but the raw seed of several members of this genus contains toxins. However, these are destroyed in the cooking process[, ].

Botanical References

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Range

E. Asia - northeast India, Myanmar, southern and eastern China, Russian Far East, Japan, Korea, Vietnam, Laos, Cambodia, Thailand

Habitat

Lakes and ponds in central and southern Japan[]. Swamps and ponds; at elevations from near sea level to 1,000 metres, occasionally to 2,000 metres in southern China[].

Properties

Conservation Status	Least Concern
Edibility Rating
Habit	Annual
Height	0.00 m
Pollinators	Self, Insects
Self-fertile	Yes
Cultivation Status	Cultivated, Wild

Cultivation Details

Trapa incisa is found mainly in subtropical climates. Plants require a high summer temperature in order to perform well, the growing plants are not frost hardy, though the seeds they produce can survive freezing winters[].
Succeeds in still or slowly-flowing water requiring a position in full sun and a slightly acidic water with a rich planting medium[].

Edible Uses

Seed - cooked. Boiled[, , ]. Some caution is advised, see the notes above on toxicity.

Medicinal

None known

Other Uses

None known

Propagation

Seed - harvest in late summer and store overwinter in a jar of water in a cold but frost-free place. The seed quickly loses its vitality if it is allowed to become dry. Sow in spring, placing one seed in each pot and submerging them under a few centimetres of water.