The Temperate Database is in the process of being updated, with new records being added and old ones being checked and brought up to date where necessary. This record has not yet been checked and updated.
Trapa japonica is a Annual
It is harvested from the wild for local use as a food.
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[
Europe to E. Asia.
Lakes and ponds all over Japan[
]. Swamps, ponds and rivers in China[
We have very little information on this species and do not know if it will be hardy outdoors in Britain. However, judging by the plants native range, it is likely to succeed outdoors at least in the warmer areas of the country. The following notes are based on the general needs of the genus.
An aquatic plant, floating by means of inflated petioles, it succeeds in still or slowly-flowing water requiring a position in full sun and a slightly acidic water with a rich planting medium[
Plants require a high summer temperature in order to perform well, they are not frost hardy[
Seed - raw or cooked[
]. Some caution is advised, see the notes above on toxicity.
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.