Deer can be lovely to look at in the wild, but when they are dining on your most valuable landscape plants they can raise the blood pressure of even the most ardent nature lover. No list of deer resistant plants is 100% trustworthy. Their tastes can change with the seasons, and with the growth changes that plants undergo each year. Sometimes it is the succulent new spring growth of a plant that they find irresistible. When that new growth hardens off later in the growing season it no longer tastes or feels the same and they move on to other delicacies. In late summer and fall, when deer are trying to accumulate more fatty tissue, they may be eating plants with higher fat content in the leaves, stems and bark.
These suggestions for plants have been observed to be less palatable to deer. These plants have also been observed to be less likely to be damaged by deer, but none of them are immune to deer browsing because under the right circumstances deer will eat almost any plant. There are many products on the market that claim to discourage and repel deer from eating desirable plants, and many of them work quite well when used according to label directions. It is probably not feasible, however, to treat an entire landscape with these sprays.
The only way to guarantee a deer free landscape is to install appropriate fencing. Since this is a costly measure to keep the deer out, it is less likely a viable option.