Monkey grass (Liriope spp.) is a fast-growing, grasslike ground cover plant that grows in both sunny and shady areas. Although the plant is an evergreen and hardy, a yellowing plant may be due to natural reasons, such as changing of the seasons and old foliage, or it may indicate a care problem.
Other than natural growth patterns, yellowing leaves may indicate that the plant is getting too much or too little water. Monkey grass stressed from drought turns yellow, and roots exposed to standing water also turn yellow. Older leaves on the play may slightly dry and wither. Natural yellowing is normal and is nothing to worry about.
Check the soil around the monkey grass to determine the problem. If the soil is overly dry several years down the plant is likely suffering from drought. If the soil around the monkey grass is sopping wet, or if the roots are brown and mushy, the plant is likely suffering from root rot. Water the plants thoroughly, about once a week, and surround the plants with mulch or pine straw to keep moisture levels high, but not soggy.
Healthy monkey grass is not overly susceptible to diseases or invasion by pests. The plant normally has dark green foliage and grows to about 2 feet tall, however exact colors and sizes may vary based upon variety.
Prune monkey grass in the late winter or early spring before growth starts. Pruning the plant too early, such as in the fall, may leave the plant susceptible to damage from the elements. Use clippers for small clumps of monkey grass, or set your lawn mower to the highest setting to remove excess foliage. Don't worry about cutting off too much foliage; the University of Tennessee Extension suggests cutting back the plant to just above the growing crown or almost to the soil line.
Make sure to prune or clip off all old or discolored foliage from the monkey grass or the plant will look raggedy for all season long. Although pruned monkey grass will initially look like it has a buzz cut, the plant will grow back healthy and normal relatively quickly.