they do it at our school to identify maintain the tree. unfortunately they are putting it on the invasive, fire-prone eucalyptus blue gums at our university, plus also bottle brush too which are all from australia and are invasive outside its range. although we also put these on our iconic native pine and cypress, in the wild they are not doing so well, because of disease, and pests, and thier range contraction. I believe the domesticated trees outnumber the wild ones.