Daughter`s Wedding

My daughter & her fiance are planning their outdoor wedding, in May, to be held at a local park. They would like to use 2 of the trees, at their designated spot that are fairly close together as a natural "arbot", using tulle. My question is how to attach the tulle to the trees at the park, without doing any harm to the trees?
Posted by Gayle; updated 02/14/10