The following note is extracted from "Birkat Ha’Ilanot: Blessing for Blossoming Trees" by Rabbi Moshe Zywica. The full version of this piece, which also contains references, can be found on the OU Kosher website here,
“Hai man denafik beyomei Nisan vechazi elanei d’ka milbalvi omer”
If one goes outside during the month of Nisan and sees trees that are blossoming, one recites the following blessing (Birkat Ha’Ilanot):
Baruch atah Adonay Elohaynu
melech hao’lam shelo chasar b’olamo kelum u’bara bo beriyot tovot ve’elanot
tovim lehanot bahem be’nay adam.
With these words we praise God’s ongoing renewal of
creation during the season of redemption in which we renew our commitment to
serving Him.
It is preferable to say birkat ha’ilanot as soon
as one sees a fruit tree in bloom, which is usually during the month of Nisan.
Some say that if you are in a country where trees bloom
earlier than Nisan the blessing can be said earlier.
If a tree blossomed in Nisan but one did not see
it until later, the berachah can still be said as long as
the fruit on the tree has not yet ripened. However, one who saw a fruit
tree in bloom during the month of Nisan but forgot or neglected to
recite a blessing may only recite it up
till when the fruit has begun to grow.
Though the blessing is said during a specific period of time during the year, it is not considered a time-bound mitzvah, so women are encouraged to say it.
