South of Zone 8 you may need to chill bulbs in the vegetable bin of your refrigerator for 12 to 20 weeks to give them sufficient chilling time to perform properly. Or you can purchase prechilled bulbs from nurseries for a slightly higher cost. Late-planted bulbs tend to produce flowers with shorter stems. Always purchase the largest bulbs you can afford. Bigger bulbs mean bigger flowers.
Healthy bulbs feel solid and heavy for their size.
Almost all spring-flowering bulbs require full sun when they're actively growing. By the time they go dormant, they can tolerate full shade. To produce picture-book flowers, bulbs must be grown in a loose, rich soil that drains well. Loosen heavy or compacted soil with a pitchfork, and add plenty of compost or shredded leaves. Specific depths for various types of bulbs can be misleading, so stick with the general rule for planting depth, which is three to four times the height of the bulb.