Answer: While no plant can be guaranteed to be "deer-proof," some types of plants are less tasty to a deer. Try planting the following kinds of plants which are less attractive to deer.
Tree suggestions include white fir, Colorado spruce, pinyon pine, common juniper, Rocky Mountain maple, hackberry and honeylocust.
Shrub possibilities are lead plant, potentilla, Austrian copper rose, quince, 'Blue Mist' spirea, winged euonymus, golden currant, lilacs, Oregon grape holly and pyracantha.
Ground covers to be tried are creeping mahonia, English ivy, thyme and snow-in-summer. Perennial flowers that may be of use are purple coneflower, peony, blazing star, Shasta daisy, Mexican hat coneflower, lily-of-the-valley and Russian sage. Deer-resistant herbs include marjoram and lavender.
Native plants growing in their native habitats may be less appealing to deer than highly fertilized and highly watered Garden plants. Any plant may be attractive to some individual deer or deer in some seasons. More extensive lists may be obtained from some municipalities or local Colorado State University Extension county offices.
Here's the website for Colorado State University's publication on deer resistant plants: http://www.ext.colostate.edu/pubs/natres/06520.html
Hope you find it helpful!
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