The second 節気 “sekki” division of the traditional Japanese calendar is:
雨水
(あまみず), (うすい)
“amamizu”, “usui”
rainwater
The final “kō” microseason within this division is:
草木萌動
“sōmoku mebae izuru”
Grass sprouts, trees bud
That makes 草木萌動 the sixth microseason of the year!
It typically lasts 1~5 March.
This is #6 in a regular subseries of 365 Days of Japanese, where every five or six days I post about a Japanese microseason that has begun around the same date as the entry. I am taking all information from the list of 72 in this article. There is also a 36 microseason list here, which may be more authentic (rather than being based primarily on Chinese sources).
Image credit: Overton Park.