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: For those in colder areas, it may be possible to "extend" the reach of marginally winter-hardy bulbs by planting in warmer 'micro-climates.' Tips: a) choose sites protected from wind and extreme cold exposure, b) mulch heavily, and c) plant deeper. It's worth a try if you really want to grow something "just beyond" your hardiness zone range.
A Sampling of Flower Bulbs for Perennializing (Return for Several Years):