Your region of relatively long cool winters, very hot to moderate dry summers and low moisture, is good for growing many bulbs, especially those native to dry climates. Though this is true for most of this large diverse region, your specific climatic conditions should be taken into account. You must especially consider major factors like high-mountain altitude, low-desert heat and sheltered valley basin environments.
Plant bulbs in the fall, starting when nighttime temperatures stay between 40-50°F. But be sure to plant approximately six weeks before the ground freezes to allow sufficient time for rooting. Flower bulbs will root best in cool soil and once rooted undergo natural changes that keep them from freezing. Water your bulbs after planting to help them start the rooting process.
After planting, apply slow release "bulb food" fertilizer on the top of the ground to supply nutrients for the second year's bloom. (Fall bulbs are already fully charged with energy for peak flowering performance in their first spring bloom season.) Do not put the fertilizer in the hole with the bulb's tender roots.
Please note: Modern bone meal often draws rodents and dogs that dig up the bulbs looking for bones!
After the ground cools or freezes, cover your beds with a lightweight mulch (pine needles, buckwheat hulls, straw, or chopped up leaves) 2 — 4 inches thick to help keep down weeds and maintain a consistently cool soil temperature.
Special Note: Because this region encompasses numerous pockets of extreme climate variance, we suggest supplementing the information here by referring to Sunset Publication's Western Garden Book or going to www.sunset.com. Both sources include information on some ten specific climates within this region.
A Sampling of Flower Bulbs for Perennializing (Return for Several Years):