Whether orange, pink or yellow, lilies (Lilium spp.) capture the eye with their vibrant colors and trumpet shapes. Their ability to reproduce through sexual and asexual means affords the gardener several ways to propagate them. Sexual reproduction is used to hybridize plants into new cultivars, while asexual reproduction methods reproduce new plants identical to the parent. Lilies grow as perennials in U.S. Department of Agriculture plant hardiness zones 2 through 9, however, some hybrid varieties are not hardy in some of the colder zones.
Reproduction by division is the least labor-intensive for the home gardener because the plant does most of the work. Division is an asexual method that only requires the parent plant to reproduce offspring. When bulbs mature, they divide and form new bulbs underground. During the next growing season, a new plant emerges from each new bulb. If left undisturbed, the bulbs will continue to divide, but they won't become invasive because overcrowding reduces the plant's size and vigor. This indicates it's time to dig up, separate and replant bulbs at appropriate spacing.
Look Into the Axil
Look carefully where the leaf joins the stem and on several varieties like tiger lily (Lillium tigrinum), hardy in USDA zones 4 through 9, you'll see tiny, black bulbils formed from asexual reproduction. These immature bulbs form roots while still attached to the parent plant. Pinch them off and plant them in pots, or directly into the ground as you would bulbs dug up from the base of the plant. Bulbils take about two years to reach bloom stage.
Scale to Propagate
Scales provide nourishment to bulbs. When peeled off, they form roots and eventually become mature bulbs. To use this method of asexual reproduction, break scales off near the base of the bulb, dust lightly with a fungicide, then place in a zip-style plastic bag with a handful of damp peat moss. Close the bag securely and place it an area that is about 70 degrees Fahrenheit. Don't place in direct sunlight; bulbs don't need sun to germinate. After a few weeks, scales grow into bulblets and form roots. Bulblets need six to 12 weeks of chilling around 40 degrees Fahrenheit in order to flower. Accomplish this by placing them in the refrigerator, or if outside temps are low enough, pot bulblets and place them outdoors. Blooms appear in about two years.
Collect the Seeds
When lily blooms are spent and fall to the ground, seed pods formed from sexual reproduction are left on the stems. Collect these pods by snipping them from stems when they turn brown and are still soft. Dry them indoors in a well-ventilated area for about three weeks, then break open the pods and collect the seeds. Lily seeds range from easy to difficult to germinate depending on the species. Easy-germinating types, or quick types, take about 18 months to bloom, while difficult species, such as Lilium speciosum, hardy in USDA zones 4 through 9, can take up to four years to bloom.