Liriope (Monkey Grass) Care: Trimming, Control, and Weed Management

Cold weather leaves liriope (monkey grass) in tatters. Edging and borders become overgrown if not kept compact. Best trim time: January–March. If lawn mower adjusts to highest setting, it can remove old greenery—new sprouts haven't emerged and won't be harmed. Wait too long and hedge trimmers are needed; cut just above new sprouts.

Q. When do I cut back liriope?

A. Sharpen shears! If bedraggled, a Marine "brush cut" helps. Look inside for new green sprouts. Use hedge shears for flat cut 3" high (or just above new sprouts). Some set mower to max height to prune old growth.

Q: Liriope sprouting all over yard in pine straw beds and English ivy. Digging and weed fabric labor-intensive; liriope finds escape routes. Best way? Can I put fabric directly over it, or will Roundup affect it?

A: You may have the "evil twin" syndrome! Clumping monkey grass (Liriope muscari) has an evil twin: spreading monkey grass (Liriope spicata). Previous owners used monkey grass for lawn edging and nature trail—clumps faithfully for ten yards, then aggressively invades ferns and azaleas for ten feet.

Similar appearance. I distinguish by leaf width: creeping liriope leaves 1/8 inch wide; clumping liriope 1/4 inch or more. Creeping liriope flowers usually white or light lavender. If you'd rather not dig, spray glyphosate (Roundup, KleerAway) three times yearly—spring, summer, fall. Monkey grass takes weeks to die but you'll gradually beat it back in a couple years. Landscape fabric likely won't work.

Q: Two kinds of liriope—one clumps, the other spreads into flower beds. Normal? Weed killer?

A: Yes, two kinds! Most know Liriope muscari—nice evergreen clump, border plant or shade groundcover. The other is Liriope spicata (creeping liriope), spreads rapidly, pest in wrong place. Creeping liriope has narrower, lighter green leaf. Both tough to control with weed killer. Best: clip leaves, wait for re-sprout, then use glyphosate (Roundup) or diquat (Next Day). Shield nearby flowers with cardboard. One spraying insufficient—constant watch until eliminated.

Q: New liriope bank invaded by grass and weeds. What kills weeds/grass without hurting liriope? Is liriope a grass?

A: Grass-B-Gon and Vantage are possibilities. Read labels for use.

Q: Weed killer to kill liriope in flower beds?

A: Liriope is tough. Waxy leaves and tuberous roots resist most herbicides. Glyphosate (Roundup) kills with two applications. Make cardboard shield for flowers. Yellowing within a week. Not all killed; spray again in a month. Clean-up spray next spring for survivors.

Q: Something eating liriope tops—rabbits or possum? Both seen in yard.

A: Likely rabbits. Cute until you see garden damage in one night. Munching won't hurt liriope unless severe. Try hot red pepper around liriope to discourage. Mowing liriope short may also discourage rabbits.

Time to mow/cut liriope. Set mower highest possible. Shortened liriope may discourage rabbits.