After the shira, the Bnei Yisrael are in Mara, unable to drink the ‘bitter’ water. Hashem instructs Moshe to put a piece of tree (a branch) into the water. After doing so, the water becomes sweet, and the Bnei Yisrael are able to drink the water.
Amazingly, this bitter branch turns the bitter water into sweet water. Essentially, this is one of the many miracles in the creation of fruit. The bracha ending we say before eating fruit from trees is ‘boreh pri ha’etz’ ‘the One who creates the fruit of the tree’. We don’t just thank Hashem for creating fruit, we also recognise the miracle of creating the fruit, something sweet, from the eitz, the tree, which has a bitter taste.
This is similarly true with ‘boreh pri ha’adamah’, where we are also recognising Hashem creating something so sweet from something so bitter, the earth
