I am starting to think deer proof plants do not exist. Apparently young deer will eat anything at least once. Here's the menu I unintentionally served up to the little darlings this summer (damages listed per incident):
Abelia "Peach Perfection" - trimmed by 50%
Bald Cypress - 75% of branches on young tree eaten
Clethra Alnifolia (Summer Sweet) "Ruby Spice" - trimmed repeatedly in various locations
Dracena Marginata - one branch gnawed off, plant not bothered afterward
Euonymus Japonicus - all leaves eaten, regrown and eaten again throughout summer
Geranium - all blooms and significant portion of leaves removed
Hibiscus - all leaves and buds eaten
Itea virginica (Sweetspire) - trimmed repeatedly in various locations
Japanese Maple - 50% of branches chewed off
Salvia "May Night" - all top growth eaten down to short bare stems
Yellow pear tomato vines - 30% of young plants eaten through open greenhouse window
Fences can help keep deer away from the garden if they are tall enough or smart enough. Most sources suggest a minimum height of six feet, but deer are sometimes known to jump over a fence at that height if there is plenty of room to land on the other side. Anything over six and half feet should provide a defense from deer jumping over and that is what I am building around my kitchen garden, but some people employ another clever approach. Deer have trouble navigating through a two layer fence even if it is low and made of a single thin twine or wire. By encircling the area to two "fences" - an inner one and another one feet away the deer have trouble with depth perception and will not attempt to enter.
I found an even simpler alternative called a Wireless Deer Fence which works as a training device to discourage deer from browsing a particular area by providing a small shock from metal prongs charged by a battery pack. The prongs sit atop a green stake containing the batteries which is stuck into the soil next to whatever plant you want to protect. The four prongs enclose a sweet scented pellet that draws in the deer. Their nose touches a prong and they feel a small shock. I have felt the shock and understand why the deer would be discouraged from eating in that area.