Bulbs are reproduced for a number of reasons. Professional gardening companies create more bulbs for commercial sale to home gardeners and professional landscapers. Private gardeners propagate bulbs to increase their stock cheaply, and flower enthusiasts multiply rare specimens for their own collections or to trade with other bulb lovers. There are several ways that bulbs can be propagated: from seed, from bulb offshoots, and from parts of the bulb.
Propagating bulb plants from seed is the easiest method to propagate bulbs. However, this method is best used when propagating a natural variety plant. Seeds of hybrid plants may revert back to one of the natural grandparent plants, rather than emulating the parent species of plant. In winter or early spring, start seeds of hearty bulbs in flats and leave in cold frames. These plants may start growing in the spring, but in some instances may not grow for two springs. Seeds of tender bulbs are best started indoors.
Healthy bulbs naturally increase by forming bulblets at the base, subdividing to form two bulbs, or forming one or more new bulbs to replace an older, dying bulb. As time goes by, a bulb's bed may become crowded. To encourage new flowering and to reduce crowding, dig up the flower bed and divide the bulbs. Move the newer bulbs to new beds as new bulb stock, and replant the older ones. Thinning bulb stock in this way is recommended for tulips and irises. However, bulblets should not be divided until they have completed one full growing season attached to the parent plant. Plant these bulblets in soil where conditions are favorable for the plant to thrive, which may mean planting them in a nursery bed for a season or two.
Bulb Cutting or Scaling
Some bulbs--such as the onion, tulip, daffodil or hyacinth--have fleshy, leaf-like layers. Injuring these bulbs will cause them to produce multiple bulblets from one parent bulb. Some examples of injuring the bulb include scooping out the inside of the bulb, scoring the bottom of the bulb, coring the bulb, or sectioning the bulb in pie-shaped wedges. In countries such as Holland, where bulb production is a major industry, this type of propagation is common. Other bulbs, such as the lily, seem to possess scales. These scales can be separated into individual bulbs that will each produce a new plant.