Liriope muscari, or Big Blue Lilyturf, is a popular evergreen groundcover favored for its toughness and ability to thrive in deep shade. Gardeners use it for edging, borders, and mass plantings due to its low-maintenance nature. Confusion often arises regarding whether this species is truly invasive. This uncertainty exists because the term “Liriope” is commonly used for two distinct species with very different growth habits, making it necessary to clarify the specific behavior of Liriope muscari.
Understanding Liriope’s Growth Pattern
The distinction between the two most common species of lilyturf centers on how they manage underground expansion. Liriope muscari is a true clumping plant, exhibiting a slow-spreading habit. It multiplies primarily by producing short, thick rhizomes that remain close to the original plant crown. The result is a gradual expansion of the clump outward, which can become dense in a garden bed, but it does not send runners far afield.
The source of the “invasive” reputation is usually the other primary species, Liriope spicata, commonly called Creeping Lilyturf. This variety possesses long, thin, and far-reaching rhizomes, which act like runners to quickly colonize new territory. The plant’s growth pattern—clumping versus running—is the factor determining whether a gardener experiences a manageable border plant or an aggressive spreader.
Ecological Classification of Liriope Muscari
The ecological classification of Liriope muscari is separate from its behavior in a manicured garden. A plant is classified as ecologically invasive when it is non-native and causes environmental or economic harm, typically by displacing native flora and fauna. Liriope muscari is non-native, originating from Asia, and is considered naturalized in many regions across the United States.
Formal assessments generally categorize it as an aggressive garden plant rather than a true invasive species. It is typically not listed as a noxious weed by state regulatory bodies, a designation for plants regulated due to their harmful potential. While some states recognize that Liriope species can be aggressive in landscapes, the plant rarely establishes widespread, dense stands in unmanaged natural areas far from where it was initially planted.
Strategies for Controlling Aggressive Spread
Containment is the most effective long-term solution for preventing the spread of running varieties like L. spicata. Installing a deep physical barrier, such as metal or plastic edging, at least 18 inches deep, can effectively block underground rhizomes from extending into new areas. For aggressive varieties, planting them initially in containers sunk into the ground can also prevent the spread of runners.
Regular division is a practical control method for both clumping and spreading types. Every three to four years, dense clumps can be dug up, divided into smaller sections using a sharp spade or knife, and then replanted. This process, best done in the late fall or early spring before new growth begins, serves to thin the planting and maintain the desired boundaries. Any portions of the root ball or rhizomes found outside the intended area should be removed.
When complete eradication is necessary, manual removal must be thorough. Digging up the entire plant, including every section of the root ball and all connected rhizomes, is the only non-chemical way to ensure the plant does not return. For persistent infestations, particularly the runner-type, non-selective herbicides containing glyphosate can be carefully applied to the foliage. Multiple applications over one or more growing seasons may be necessary, as the robust rhizome system requires repeated treatment for full elimination.