Daylilies (Hemerocallis) are durable perennial plants known for their resilience and colorful summer flowers. Their vigorous growth habit eventually leads to overcrowding. Periodically thinning these dense clumps is necessary maintenance that rejuvenates the plant and restores its ability to produce abundant, high-quality blooms.
Identifying When and Why to Divide
The necessity of division is signaled by changes in the plant’s appearance and performance. A decline in the size and quantity of flowers is the most visible sign that the root system is over-congested. The central foliage may begin to thin or die out, creating a noticeable “doughnut” shape as the older center becomes unproductive. When the root mass grows too dense, plants compete intensely for limited soil nutrients and moisture, resulting in weak growth and smaller blooms.
Most daylily cultivars benefit from being divided every three to five years to prevent self-crowding. The best time for this procedure is either in the very early spring as new shoots emerge, or in the late summer or early fall after flowering concludes. Dividing during these cooler periods minimizes transplant shock, allowing new divisions time to establish roots before summer heat or winter dormancy.
Step-by-Step Guide to Thinning and Separation
Begin preparation a day or two prior by thoroughly watering the clump to hydrate the roots and soften the soil. Before digging, trim the foliage back to approximately six to twelve inches to reduce transpiration and make the root ball manageable. Use a sturdy garden fork or spade to dig a circle six to twelve inches away from the foliage perimeter, working deeply beneath the entire root mass.
Once the root ball is loosened, gently lift the entire clump from the ground, preserving as much of the fleshy, tuberous root system as possible. Remove the soil so the individual fans (plant units) can be clearly seen. This is accomplished by shaking off loose soil or rinsing the root ball gently with a garden hose. With the crowns exposed, begin the separation process using firm but careful force.
The clump can often be pulled apart by hand, starting from the outside edge. Very dense masses may require two garden forks placed back-to-back or a sharp, clean knife to slice through the intertwined roots. The goal is to create separate divisions, each consisting of a healthy root system attached to at least two or three leaf fans. Discard any sections that appear old, woody, or have deteriorated roots, as they will not produce vigorous new growth.
Replanting and Immediate Care
After separation, prepare the new location for successful establishment. Dig a planting hole slightly wider than the root spread and deep enough to accommodate the roots without bending. Mixing compost or aged organic matter into the bottom of the hole improves drainage and nutrient availability for the developing root system.
When placing the division, create a small soil mound in the center and spread the roots over it. Position the plant so the crown rests at or slightly below the surrounding soil level (about a half-inch to one inch deep). Planting the crown too deeply can lead to rot, while planting too shallowly causes the roots to dry out. Backfill the hole gently, firming the soil around the roots to eliminate air pockets.
Cut the remaining foliage on the newly planted divisions back to a height of about six to eight inches. This trimming helps the plant dedicate energy to establishing a new root system. Immediately after planting, water the divisions thoroughly and deeply, ensuring the root zone is saturated. Apply a two-to-three-inch layer of organic mulch around the plant, keeping it away from the crown, to regulate soil temperature and conserve moisture.