Yes, daylilies (Hemerocallis spp.) are prolific spreaders. From a botanical perspective, their vigorous growth and colonization of garden spaces are driven by specific physiological adaptations and reproductive strategies. Their spreading habit is a key to their survival and success as a perennial plant.
The primary way daylilies spread is through their root system. They grow from fleshy, fibrous roots that produce specialized underground stems called rhizomes. Rhizomes are stems that grow horizontally just below the soil surface. These stems store energy in the form of carbohydrates, allowing the plant to survive winter dormancy and fuel rapid growth in spring. Each growing season, the rhizomes elongate and produce new growing points, called "fans" or "shoots." Each fan is a collection of leaves that can become an independent plant. Over time, a single daylily plant expands outward from its original planting location, forming a large, dense clump as these rhizomes continue to branch and produce more fans.
While vegetative spread via rhizomes is the most significant factor in a garden setting, daylilies also spread sexually through seeds. After flowering, if the blooms are pollinated, they will produce seed pods. Once mature, these pods dry out, split open, and release seeds. These seeds can be dispersed by wind, water, or wildlife to new areas of the garden. However, it is important to note that many modern hybrid cultivars are sterile and do not set viable seed, making rhizome growth their sole method of expansion. Furthermore, daylilies grown from seed will not be identical to the parent plant due to genetic recombination.
To manage their vigorous growth and prevent them from overtaking other plants, several control methods can be employed, each targeting their reproductive strategy.
Physical Division: The most effective method for controlling a daylily clump is regular division. This process involves physically digging up the entire plant every three to five years and using a sharp spade or knife to cut the mass apart. Each division should have at least two or three fans and a portion of the healthy root system. This not only controls the plant's spread but also rejuvenates it, encouraging more vigorous blooming.
Edging and Root Barriers: Installing physical barriers in the soil around a daylily planting bed can help contain its lateral rhizome growth. Sinking landscape edging or a root barrier 12-18 inches deep around the perimeter creates a wall that the rhizomes cannot easily penetrate.
Deadheading: To prevent spreading by seed, simply remove spent flowers (deadhead) before they have a chance to develop into seed pods. This redirects the plant's energy back into root and foliage growth instead of seed production.
Container Gardening: For ultimate control, growing daylilies in pots or other containers physically isolates their root system and completely prevents underground spread into other garden areas.
