Tree Watering Part 2

Photo from Tree Gator

I have seen municipalities use bags to water their trees. (It seemed like a good idea to me, but I checked with one of our arborists to make sure there weren't any downsides--none came to mind.)

A quick Google search revealed several different options of tree watering bags, from DIY instructions to manufacturers selling different models. If I were going to try one, I would stick with the "doughnut" shaped bags. More conical options that reach higher on the trunk worry me as far as rotting.

Have you tried a "water bag"? What did you think?