Liriope – Spreading Monkey Grass vs Clumping Monkey Grass
Q: I’m having a terrible time with liriope that is sprouting up all over my yard. Most of the landscape is either pine straw beds or English ivy. I have begun digging up patches of the liriope and then putting down weed fabric covered with straw. This is very labor intensive and the liriope still seems to find escape routes. What is the best way to tackle it? Can I just put the weed fabric directly over it without digging it up ?
A: You may be dealing with the “evil twin” syndrome! Like Dr. Jekyll & Mr. Hyde, “clumping” monkey grass, Liriope muscari, has an evil twin: “spreading” monkey grass, Liriope spicata. The previous inhabitants of my house were unaware of this when they used monkey grass to line the front lawn and backyard nature trail. Along the trail, the liriope clumps faithfully for ten yards but at one spot it aggressively invades my ferns and azaleas for ten feet from the trail.
The two are very similar in appearance. I tell them apart by the width of the leaf: creeping liriope has leaves only one-eighth inch wide, clumping liriope leaves are one-fourth inch or more in width. Creeping liriope flowers are usually white or light lavender.
If you’d rather not dig it up, you can achieve control of either liriope with a bit of patience. Spray it with glyphosate (click for sources) three times a year, in spring, summer and fall. Monkey grass will take several weeks to die but you will gradually beat it back in a couple of years. I doubt that covering it with landscape fabric will work.