Damage

• When deer eat the buds from young walnut trees, they essentially force the tree's growth habit to change, causing the branches to fork undesirably. Trees are usually left stunted and deformed. Those that aren't properly cared for after the damage occurs are more likely to be weakened by stress and may die as a result of competition from weeds. In addition, wounds to the bark are always an entry point for plant pathogens that are fatal to the tree. Landscape trees that are valued as ornamentals, of course, are far less likely to be left on their own to recover.
  
  

Prevention

• The only way to keep deer off your property is to surround the entire area with a fence at least 8 feet tall, but hungry deer can clear even a fence that tall if they really need to eat and you've got a tasty young tree on the other side. The fence method is also extremely impractical. Try laying landscape wire on the ground around the base of the tree. You'll have to cut the wire so it fits around the tree and extends on all sides at least 2 or 3 feet from the tree's longest branch. Deer tend not to like stepping on such a thing and it may successfully keep them away. But again, hungry deer aren't likely to let such things keep them away from food.
  
  

Pruning

• Knowing how to prevent deer from accessing your young walnut trees probably isn't as effective as knowing how to care for them once they're damaged. You'll have to prune the tree so it maintains its central leader if the deer clipped any buds that might cause the central branch to fork. Prune out broken branches back to healthy wood. Make sure all terminal buds are facing outward so no new branches grow inward.
  
  

Stress Relief

• The most important steps you can take are those that relieve stress on the tree. The tree will need weekly watering, an application of an all-purpose granular fertilizer that can be watered into the root zone and a layer of mulch a few inches thick that extends out to the drip line and begins at least 6 inches from the trunk to prevent rot. A strong tree will be able to withstand and recover from future attacks.