Tree shelters do more than just protect the seedling from deer, mice, voles and rabbits. They act as a greenhouse, collecting light and warming the temperature inside the shelter for earlier growth in the spring and later growth in the fall. Shelters act as markers, making the trees easier to see. This allows quicker inspection and maintenance. Being visible also prevents the tree from being mowed by a careless operator. Tree seedlings planted into pasture sod without shelters had 70% mortality whereas tree seedlings with shelters had 30% mortality.
Research and experience indicate that shelters increase survival and growth in newly planted tree seedlings.