That's a good point. I was thinking I should irrigate it for the first couple years to help it get a really good root system, and longer if it seems they need it in the place I have to put them. They sure love water! One summer when we had extreme heat for this area we watered the ones we have near our garden, and they did very well that year. Seems like a good investment to help increase the 'crop yield'.
I have a white mulberry that volunteered. My experience is that the rabbits like it fresh okay but not nearly as much as they like the willow. However, they go after it dry as fast as they do the dry willow. I just pruned the tree and put the branches in feed bags and that worked but as I said earlier, I live in a very dry area.