Another plant we love to sing the praises of: evergreen, usually compact, deer resistant and drought tolerant - with flowers that last 3 months or more. The only thing you have to do to enjoy them is to not overwater, and to prune the flower stems back to the base of the plant after blooming is done.
This photo shows a Euphorbia characias variety in full bloom, with Allium 'Purple Sensation' in the foreground. Flowering begins in early spring and will easily last into July. The flowers are set off by the larger bracts, thus lasting longer than a typical petaled flower. When flowering stalks start to brown or look faded, just prune the flower stem all the way to the ground so the new stems can fill in.
As an added bonus, Euphorbias are evergreen in all but the coldest Rogue Valley winters, and their foliage tends to color up in winter; providing a nice visual interest in the winter garden. Euphorbias will take full sun to half a day of sun and need well draining soil. They all have a white sap in their stems keeping the deer at bay but can also cause a rash in some people, so wear gloves when pruning Euphorbias.
There are many, many varieties of Euphorbia, here are some of our favorites: