The Haiku is by Ransetsu Hattori (1654-1707), one of Basho’s students.

It reads: “Ume ichirin, icihirinhodono atatakasa”

Ume is Japanese plum, and in this Haiku most likely a winter plum.
One can translate as follows:
"One plum flower is blossoming.
It is only one blossom but we can feel the warmth.”
(of the spring approaching)

Translation by Naoko Motojima