Asiatic lilies are popular garden flowers, known for their vibrant, upright blooms and ease of care. These perennials reliably return each year, adding color to the summer landscape. They do not spread aggressively across a garden bed. Instead, Asiatic lilies increase their presence by forming dense clumps rather than invading new territory via expansive root systems.
The Difference Between Spreading and Clumping
Plant growth habits define how a plant expands in the soil. A “spreading” plant, such as mint or certain bamboo, uses specialized horizontal stems (rhizomes or runners) to aggressively colonize new areas. These underground structures rapidly extend away from the parent plant, sending up new shoots that are often difficult to contain.
Asiatic lilies are “clumping” plants. Their multiplication is localized and predictable, staying confined to the area immediately surrounding the original bulb. New growth emerges directly adjacent to the parent, resulting in a tighter cluster of stems over time. This contained habit means Asiatic lilies are well-behaved in a mixed perennial border.
How Asiatic Lilies Naturally Multiply
The primary method of multiplication for Asiatic lilies is the asexual production of bulb offsets, or bulblets. The parent bulb, a fleshy, underground storage organ, produces these miniature daughter bulbs directly from its base. These offsets develop their own roots and foliage, growing into mature, flowering plants right next to the original bulb.
This process leads to the dense, localized grouping characteristic of Asiatic lilies. A single mature bulb may generate two to four new bulbs annually, slowly increasing the size and density of the clump. This bulblet formation is a slow, steady, and reliable method of increasing the plant’s stock, unlike the aggressive root travel seen in spreading species.
Asiatic lilies can also reproduce sexually through seeds, which form in pods after the bloom fades. Seeds are not the main way they multiply in a managed garden because they take three to seven years to produce a mature, flowering plant. Additionally, since most Asiatic lilies are hybrids, the resulting seedlings may not resemble the parent plant.
When and How to Divide Lilies
While the clumping habit is desirable, the resulting density eventually requires intervention to maintain plant health and optimal flowering. Division becomes necessary when bulbs become overcrowded, typically every three to five years, causing competition for water and nutrients. A decrease in flower size or quantity signals that the clump needs thinning.
The best time to divide Asiatic lilies is in the early fall, after the foliage has died back, or in the very early spring before new growth emerges. This timing allows the bulbs to store maximum energy and reduces transplant shock. To begin, cut the stems back to about six inches above the soil line and carefully dig a wide circle around the clump to avoid damaging the bulbs.
Once the clump is lifted, gently separate the mature bulbs from the smaller offsets. Replant the larger, main bulbs immediately, spacing them eight to twelve inches apart and planting them four to six inches deep. The smaller bulblets can be planted an inch or two deep in a separate nursery bed to grow to maturity.