Daylilies (Hemerocallis) are a beloved perennial flower, known for their vibrant colors and remarkable hardiness. While these plants are exceptionally low-maintenance, they are also vigorous growers that eventually require division to maintain their health and flowering performance.
Identifying the Need for Division
Daylilies signal that they need division through several noticeable visual cues, typically after they have been established for a few years. A general guideline is to divide clumps every three to five years, though some varieties can tolerate longer periods before becoming overcrowded. The most common sign is a significant reduction in the size or number of flowers produced, even when the plant receives adequate water and sun.
The dense root system eventually competes too heavily for nutrients and water. Overcrowding can cause the center of the plant to become woody and unproductive, leading to a visual “doughnut effect” where the foliage dies out in the middle. This lack of vigor and the thinning or yellowing of foliage indicate that the plant’s roots are struggling to support the entire mass. Dividing the plant at this stage alleviates the competition and promotes renewed, healthy growth.
Optimal Timing for Division
The best time to divide daylilies is when the plants are not actively growing or flowering, minimizing stress and allowing for root establishment. This leaves two primary windows for successful division: late summer/early fall or early spring.
Dividing the plants in late summer or early fall, immediately after they have finished blooming, is the preferred time. This timing allows the newly separated divisions approximately four to six weeks to establish their root systems before the first hard frost arrives. The cooler temperatures of early autumn reduce transplant shock, and the established roots are prepared to support vigorous foliage and flower growth the following spring.
In early spring, just as new growth begins to emerge but before the weather turns hot, is the alternative window. Dividing at this time makes the clump easier to manage since the foliage is short and manageable. However, spring division may sacrifice some or all of the current season’s blooms, as the plant must dedicate its energy to root recovery rather than flower production. In regions with extremely hot summers, a spring division is sometimes preferred because it avoids the intense heat stress that can severely damage a newly planted division in late summer.
Steps for Successful Division and Replanting
Lifting and Preparing the Clump
Thoroughly water the daylily clump the day before division to ensure hydration and easier digging. Use a garden fork or spade to dig a circle about 8 to 10 inches away from the perimeter of the foliage. Gently lift the entire root mass from the ground. Once lifted, the excess soil should be gently shaken or rinsed off the roots to expose the crown and root structure.
Separating the Divisions
Separate the dense root ball into smaller, viable divisions. You can sometimes gently tease apart the fleshy roots by hand, especially if the clump is not severely matted. For older, more congested clumps, you may need to use two garden forks inserted back-to-back, or a sharp knife or spade, to cut the clump apart. Each resulting division should have at least one to three “fans” of leaves and a good portion of the root system.
Replanting the Divisions
Before replanting, trim the foliage back to about 6 to 8 inches in height to reduce moisture loss and stress on the roots. Dig a hole that is wide enough to accommodate the spread of the roots, and amend the soil with compost if needed. Create a small mound of soil in the center of the hole. Spread the roots over the mound and position the division so the crown—where the leaves meet the roots—sits just below the soil surface. Fill the hole, gently firm the soil, and water deeply to remove air pockets. Consistent watering for the first few weeks is necessary to support the new divisions while they establish.