They can be left in the ground until they need to be divided. Hardy bulbs can be purchased in many types of stores and from mail order nurseries. The best results are obtained with good quality bulbs.
Healthy bulbs are firm, relatively unblemished and show no signs of rot.
Buy enough bulbs of the same variety to assure a good show. Plant all the bulbs of one variety together for uniformity of height and time of bloom. Buying a mixture of different colors may lead to disappointment. When planting there is no way to tell what bulb produces what color flower. The mixture may be made of different colors and types.