Deer are persistent and hungry creatures. They will browse off of even the least palatable tree if they are hungry enough. They may cause browsing damage by eating tender buds or peeling bark. They may cause even more problems during mating season by rubbing their antlers against tree trunks to rid them of velvet, tangling antlers with trees (to make noisy displays toward other males) or rubbing trees to mark them with scent. Deer are quite intelligent and determined. Attempts to repel deer may need to be repeated, persistent and used in combination to have a lasting effect.
Erect a barrier, such as fencing. Fences will help keep deer away from plants, but they have to be very tall to prevent deer from leaping over the top. A less expensive (and possibly less labor-intensive) method involves protecting each individual tree.
Place the loose end of your fence roll around the tree to rough out a measurement. Fold the welded wire or chicken wire fencing around on itself to size the cylinder. Leave enough space between the tips of the branches and the fence itself to prevent deer from being able to feed through the wire (at least three inches). The height and width of the tree will determine the length of fence needed.
Cut vertically through the wire to free it from the roll. Use the cut ends to attach the fence to itself, forming the cylinder.
Cut a piece of wire to cover the opening at the top of the cylinder. Use plastic ties or the rough cut ends of the fence piece to attach the top to the cylinder.
Cut away the horizontal connecting pieces, leaving several inches of vertical wire to sink into the ground at the bottom end of a welded wire cylinder. Set the cage over the tree and press the wires into the ground. Simple body weight pressure should suffice.
For chicken wire, you can secure the fence with tent stakes. In more extreme cases, you may need to bury the bottom edge of the fencing to keep deer from knocking over the fencing.
Try a sulfur, ammonia, garlic or hot pepper spray. Apply it directly to foliage. These sprays can be made or purchased and have successfully deterred deer from feeding on plants.
Apply repellent to rags, then hang or drape them around the plant needing protection. The University of Minnesota Extension Service suggests the use of a repellent called thiram, which can be applied to trees directly.
Apply your chosen repellent repeatedly. Sun, snow and rain all act to wear away these sprays, so they must be applied weekly (or more often, if conditions warrant).