Spider grass, also known as monkey grass, liriope or lilyturf, is often grown as an ornamental border plant. Unbeknownst to most gardeners, there are two types of spider grass. One (Liriope muscari) is a well-mannered clumping variety, while the other (Liriope spicata) is a creeping variety. Once in the ground, this variety of spider grass will spread all over your yard. Despite its creeping habit, spider grass is fairly easy to get rid of with a couple of control methods applied consistently.
Dig up all of the offending spider grass plants. Be sure to remove all of the underground roots you can find. Even small root pieces can regenerate to form new plants. Discard all removed foliage and roots immediately.
Spray any re-sprouting plants with a glyphosate herbicide. Follow the manufacturer's instructions and coat all of the plant's foliage until just before the point of runoff. The sooner you spray the plants the better. Before you spray, protect any adjacent plants by covering them with plastic. Glyphosate is a non-selective herbicide that will kill any plant it touches.
Re-spray the plants once in spring, summer and fall until the spider grass stops coming back. This may take several seasons.