Hilchos Geirushin 1:7

We may not even write the boilerplate part of a get on something that is still attached to its source of nourishment. Let’s say that someone did write the boilerplate part of a get on something that was still attached to its source of nourishment. He subsequently detached it and filled in the names of the man and the woman, the date, and the operative phrase, “you are permitted to any man,” after which it was signed by the witnesses. In such a case, the get is valid after the fact (b’dieved).

Hilchos Geirushin 1:8

If a man writes a get on a leaf growing in a flowerpot that is perforated at the bottom (and therefore considered to draw its nourishment to the ground), the get is invalid even if he gives his wife the entire flowerpot. This was enacted out of concern that he might detach the leaf. One may, however, write a get on the flowerpot itself and give that to her.