Taking unable blossom Changsha water spinach（Ipomoea aquatica）under natural growth
condition as test material，this paper measured the critical photoperiod，limited inductive photoperiod and juvenile
phase of Changsha water spinach by light transfer method．The results showed that the critical photoperiod of
Changsha water spinach was 12 hours light/12 hours dark，limited inductive photoperiod was 16 days，and the
juvenile phase of Changsha water spinach would terminate at 4-leaf stage．Additionally，when the dark period of
photoperiod sustained to 13 hours，it was more conducive to the flower bud differentiation in Changsha water spinach．
While the differentiated flower bud would be reversed，if the induced photoperiod was less than limited inductive
photoperiod．These results indicated that Changsha water spinach was strictly an obligatory short-day plant.