花了不少時間查究，只肯定牠是荸薺屬，品種有點像 eleocharis parvula。
these spikesedge look fascinating, almost like from the outer-space. i met them at the wetland park last month.
spent some time checking out what species they are and couldn’t be sure. the only certain fact is that they are from the genus of eleocharis.
eleocharis is a genus of flowering plants in the sedge family, cyperaceae. water chestnut is one big representative.
eleocharis are known commonly as spikerushes, or more technically as spikesedges. their habitat is generally at wetland or aquatic. they are easily recognizable as they have photosynthetic stems and lack leaves (the leaves have been reduced to sheaths surrounding the base of the stems). wiki
荸薺屬 eleocharis – kingdom plantae 植物界 | (unranked 未分級): angiosperms 被子植物 | (unranked 未分級): monocots 單子葉植物 | (unranked未分級): commelinids | order: poales 禾本目 | family: cyperaceae 莎草科 | genus: eleocharis 荸薺屬 wiki