So to handle the weeds on our organic farm they burn them. It's really quite interesting to watch, and when Brendon saw it being done for the first time yesterday morning he ran out there with the camera.
The flame looks enormous in real life, and it just eats up the weeds like candy and then dies out immediately after. It burns too hot and fast to be of any damage to the trees.
Also notable fire fun is burning rice fields after harvest.