Hilchos Sukkah

The Gemara in Sukkah says that the sechach that one must use for his sukkah must be detached from the tree in order for it to be fit for use. The Gemara (Sukkah 11a) discusses what a person must do if one put branches on his sukkah before they were cut off from the tree. The Gemara concludes that branches must be detached from the tree and he then must shake them.