Garden lilies provide elegant colour beginning with bright Asiatic hybrids in June, through summer's regal Orientals and early fall's towering tiger lilies. The lovely lily is a tough customer, too. It grows from bulbs that not only bear nutrients for the succeeding season but act as vegetative propagation backup if seed production fails.
Multiplication by Seed
Lilies, like other flowering plants, propagate sexually by growing seeds in ovaries after pollen is transferred by passing insects, animals or weather from stamens to the central pistil. Successfully fertilised seeds ripen in pods throughout the summer and fall to the ground when the lily stalks die back in early winter. New plants rise from seeds the following spring if conditions are right, but plants may have to grow for two or three years before bulbs form and become large enough to support blooms. Species lilies multiply by seed annually but some hybrid lilies set seed only occasionally.
About Lily Bulbs
Garden hybrid lilies and the wild, or species, lilies from which they are descended grow from true bulbs, The lily's tunicate bulb grows from the interior and the outer layer, or tunic, dries and protects the growing bulb. Most lilies have energy left over to create new bulbs from which new lily plants rise. New bulbs grow larger each year until their plants also bear blooms. As new bulbs become larger, though, more bulbs compete for a finite amount of nutrients and bloom declines. Lilies take differing periods of time to multiply by vegetative propagation according to species and whether plants start from bulbils, bulblets or mature bulb divisions.
Bulbils and Bulblets
Some types of lilies, such as tiger lilies, grow tiny bulbils in the notch formed at the intersection of leaves with the plant's singular stalk. It might take a seed a year to develop into a tunicate bulb but bulbils grow yearly. In fall, bulbils fall from the plant and begin developing roots that will pull them into the ground before winter. Another junior bulb, known as a bulblet, grows around the base of the parent bulb or on the underground portion of the lily plant stalk. Bulblets are the ultimate backup: they strip away from a stalk or bulb pulled out of the ground by a hungry animal or careless gardener and scatter. Within a year or two, new plants grow large enough to bloom.
Left alone, bulblets grow unto bulbs and grow new plants next to the parent. For this reason, gardeners choose to lift and divide bulbs to move newly mare bulbs to bloom in new positions and keep plants blooming in the original space. How often gardeners lift bulbs depends on the rate of creation and growth of bulblets that form around the base of the tunicate bulb. Most Asiatic and Oriental hybrids will form clumps that bloom for many years before bloom declines. Some are ready for splitting after two or three years. Mature bulbs bloom the summer following division.