Deer-resistant plants, says the Oregon State University Extension, are not deer-proof plants. Even so, choosing deer-resistant plants for your Idaho landscape may encourage deer to browse elsewhere. Idaho's deer-resistant plants include trees, shrubs, vines, perennials and bulbs that flower at different times of year. Select them accordingly to have continuing garden color with minimal interference from the Gem State's herds of hungry deer.
All varieties of monkshood, according to the Rutgers New Jersey Agricultural Experiment Station, rarely suffer deer damage. Idaho's Columbian monkshood (Aconitum columbianum), standing from 2 to 6 feet high, grows wild along stream banks and in moist thickets and woods. A tuberous perennial, it has green leaves along its straight, strong stems. In July and August, the stems have airy spikes of deep-blue hooded blooms. Lower flowers open first. Columbian monkshood is a bumblebee and hummingbird favorite. Plant the tubers, says the Lady Bird Johnson Wildflower Center, in a shady location with moist, rich soil. Like those of all members of the Aconitum genus, every part of this plant is toxic if ingested.
Perennial snow-in-summer (Cerastium tomentosum) likes full sun and dry soil. Standing up to 1 foot high and wide, this mat-forming plant makes an excellent ground cover, says the Missouri Botanical Garden. Its silvery leaves grow up to 6 inches high. Flower stems appear in late spring, rising 6 inches above the leaves. In June their clusters of 1-inch white blooms create the illusion of fallen snow. The "Yo-Yo" cerastium cultivar is a less invasive plant than its wild relative.
Plant summer-in-snow in full sun and and sandy, dry well-drained soil. Drainage is more important than soil type; plants in poorly drained locations are nearly certain to develop root rot. In Idaho's cool summers this plant spreads rapidly. Cut back its dead flowers to prevent it from self-seeding and prolong its foliage.
Winter-hardy in Idaho's USDA Plant Hardiness Zones 5 through 7--much of the western and northern parts of the state--bluebeard (Caryopteris x clandonensis) belongs to the verbena family. It's a small flowering shrub growing between 2 and 3 feet high and wide, sometimes called blue mist or blue spirea. It has lance-like, aromatic silvery leaves that drop off in the fall. Between June and September, the shrub's airy blue flowers give it a misty appearance. They are a magnet for butterflies and bees.
Plant bluebeard in full sun and well-drained loam. It will not tolerate poor drainage. Massed plants make stunning displays, say the Missouri Botanical Garden. Stems that die back in winter will return in the spring. Even plants that do not die back will benefit from hard spring pruning to promote the new growth that produces flowers.