What is the beracha for bananas?
On bananas one recites ha’adamah. Please see sources.
Bananas are perennial plants whose new fruit grows directly from the root every year.
Whether the bracha on bananas depends on a dispute among rishonim. According to the Rosh, the bracha recited is ha’eitz since the root remains from one year to the next. However, according to the opinion of Tosafos and of Rashi, the bracha is ha’adamah, since the part of the plant that is above ground does not produce fruit again.
Due to the uncertainty, one should recite ha’adamah. This is because someone who mistakenly recites borei pri ha’adamah on a fruit that should have been borei pri ha’eitz fulfills the minimal requirement bedieved and should not recite an additional bracha of borei pri ha’eitz.
The Shulchan Aruch and the Rama (Orach Chayim 202:2) rule that the bracha on perennials whose stem dies each year is ha’adamah.
However, it is disputed whether the reason we recite ha’adamah is because the Shulchan Aruch concluded like Tosafos and ha’adamah is indeed the correct bracha, or because it is a safek whether the bracha should be ha’eitz (like Rosh and Tur), or ha’adamah (like Tosafos), and we recite ha’adamah because of this uncertainty (Maamar Mordechai; see also Graz and Aruch HaShulchan).
The practical difference is for somebody who recited ha’eitz on a banana (whether he needs to recite another berahcha, or can rely on the ha’eitz).