Lily bulbs are perennial and multiply over time, creating dense clumps that require periodic division for plant health and continued vibrant displays. This process, often called splitting or dividing, prevents overcrowding, which can severely reduce the quality and quantity of future blooms. Division is a necessary maintenance task that rejuvenates established plants and offers a simple, effective method for propagating new ones. Understanding when and how to perform this task ensures your lilies remain a spectacular feature in your garden.
Signs Your Lilies Need Dividing
The primary indication that your lilies require division is a noticeable decline in their flowering performance. While a healthy clump should produce robust blooms annually, an overcrowded clump will exhibit reduced flower production or smaller, less impressive individual blossoms. This reduction occurs because the dense mass of bulbs and roots competes intensely for limited soil nutrients and moisture.
You might also observe general signs of plant stress, such as weakened stems or a high concentration of stunted growth within the cluster. If the foliage becomes overly dense, making it difficult to distinguish individual plants, or if the center of the clump appears to be thinning, it is a clear signal that the underground bulbs are competing for space. Most varieties, particularly the fast-growing Asiatic hybrids, benefit from division every three to five years to prevent these issues.
Ideal Timing for Splitting Lily Bulbs
The optimal time to divide and replant lily bulbs is in the early fall, typically from late August through September, after the plant has finished flowering for the season. This timing is preferable because the foliage has begun to yellow and die back, indicating that the plant has stored maximum energy for the next growing cycle and is entering a period of semi-dormancy. Working with the bulbs while they are dormant minimizes transplant shock and allows the newly separated bulbs time to establish new roots before the first hard frost arrives.
While division can be done in the early spring before new shoots emerge, fall is superior because it maximizes the time the bulbs have to settle into their new locations. Lily bulbs do not enter a state of complete dormancy, which means they must be replanted immediately after being lifted. Replanting in the fall ensures the bulb is fully prepared to focus its energy on flowering once the active growing season begins in spring.
Step-by-Step Guide to Division and Replanting
The process begins by carefully digging up the entire clump, using a garden fork or spade 6 to 12 inches away from the main stems to avoid damaging the bulbs. Gently lift the mass and shake off excess soil to expose the network of bulbs and roots. You will see the larger, older “mother” bulbs surrounded by smaller offsets, or bulblets, which are the new plants.
Separate the individual bulbs and bulblets by hand, gently pulling them apart or using a clean, sharp knife to slice between dense sections if necessary. Inspect each bulb for any signs of disease, rot, or damage, discarding any that feel soft or mushy. Only firm, healthy bulbs should be replanted into a site that is ready, ideally with well-draining soil amended with compost or organic matter.
Replant the larger, mature bulbs about 4 to 6 inches deep, while smaller bulblets only need to be planted 1 to 2 inches deep. Ensure the pointed end of the bulb is facing upward and the roots are spread out below. The newly planted bulbs should be spaced approximately 8 to 12 inches apart to allow for several years of future growth without immediate re-crowding.
Post-Division Care
Immediately after replanting, water the area thoroughly and deeply to help settle the soil and eliminate any air pockets around the roots. Adequate moisture is necessary for root establishment, but the soil must be well-draining to prevent the fleshy lily bulbs from rotting. This initial watering is crucial for reducing the stress of the transplanting process.
Applying a generous layer of organic mulch, such as straw or shredded leaves, over the newly planted area provides insulation and helps to regulate soil temperature and moisture levels throughout the winter. The mulch also delays the ground from freezing solid, allowing the bulbs a longer period for root growth before the cold weather fully sets in. Due to the energy expended on root development, expect the newly divided bulbs, especially the smaller offsets, to produce fewer or no blooms in the first year as they focus on becoming established.