The shehecheyanu blessing is recited, in addition to the regular blessing, whenever doing something for the first time that year, like doing a mitzvah, such as the first lighting the Chanukah candles, reading the Megillah on Purim, and taking the lulav and etrog on Sukkot.
In addition the first time each year one eats a fruit or vegetable which is seasonal, i.e., one which grows only at a certain time of the year, the fruit is considered a "new fruit" and this special blessing is recited.
The shehecheyanu should preferably be said before the regular blessing on the fruit, although some have the custom to say it afterwards. The blessing is said only if the fruit is ripe (not dried). Examples of seasonal fruits over which one can say this blessing: kiwi, fresh figs or dates, pomegranates, cherries, tangerines, cantaloupes, and strawberries.
Ba-ruch A-tah A-do-noi E-loi-hei-nu
Me-lech ha-o-lam she-he-chee-ya-nu v'ki-yi-ma-nu
vi-hi-gi-ya-nu liz-man ha-zeh.
Blessed are You, L-rd our G-d, King of the
Universe, who has granted us life, sustained us and
enabled us to reach this occasion.
Listen to the recitation of the Shehechiyanu blessing