Someone who goes out in the days of Nissan and sees [fruit] trees that have blossomed flowers, says, “Blessed are you Hashem,...who fashioned good creations and good trees for people to enjoy...” [Shulchan Aruch O.C. 226:1]
Bircas Ilanos is said in Nissan, By every girl and boy, We thank Hashem for the beauty, That He made for us to ______.