Moss in a lawn is not necessarily a bad thing. Usually moss becomes established in lawn areas where turf is thin or nonexistent. This may be a shady or full-sun site that remains wet for long periods of time. Areas with poor surface drainage, like low spots that collect water, or poor air circulation found next to buildings or wooded lots may also have moss. In these cases, it is not so much that the moss is crowding out the grass but rather the moss is filling in as the grass thins out.
If the problems causing poor turf cannot be corrected, then consider moss as a natural ground cover to be protected. Mosses are very short, primitive-branched plants that often produce a dense, green, felt-like mat over the soil surface. They serve to help stabilize the soil and cover an otherwise unprotected soil surface.
However, if you prefer a turf lawn, the mossy area will need to be renovated and reseeded. A flail-type dethatcher will remove or dislodge most moss. Moss may be killed with copper sulfate or iron (ferrous) sulfate. As a desiccating agent, hydrated lime will also kill moss. A new product, QuickSilver T&O by FMC Corporation, is effective at selectively controlling moss in fescue, as well as many broadleaf weeds, without damaging the turf.
Even if the moss is killed, it will rapidly recolonize areas unless the conditions causing the poor turf are corrected. Permanent moss control can only be achieved by improving the growing conditions. Cultural practices that favor a dense turf in areas subject to moss evasion include:
- When possible, prune the lower limbs of trees and remove or thin underbrush to improve air circulation and allow more sunlight to the surface.
- Improve soil surface drainage by recontouring the surface to prevent puddling.
- Improve subsurface or internal drainage by installing a perforated drainpipe encased in gravel.
- Establish only the most shade-tolerant grasses such as a turf-type tall fescue or a fine fescue. Seed during late August or September to assure good establishment. In heavy shade, where turfgrasses are impossible to maintain, consider establishing an evergreen ground cover. Even turf-type perennial ryegrasses make an excellent temporary turf in heavy shade. Also in heavy shade consider establishment of ferns or native wildflowers, or cover the entire surface with suitable mulch.
- Always remove fallen tree leaves periodically during late fall.
- Raise the mowing height to 2-1/2 to 3 inches and mow as frequently as needed to remove less than 1 /3 to 1 /2 of the leaf area in any one mowing.
- Do not over-fertilize with nitrogen. In wet soils and or shady conditions, more than one or two nitrogen applications per year will develop a disease-susceptible turf that will seldom survive past mid-summer. However an application of nitrogen at in late October or early November helps to increase the turf density.
- Do not over irrigate. Turf susceptible to moss invasion seldom needs irrigation. Always avoid light, frequent irrigations and do not water in late afternoon or night if you are trying to avoid a moss buildup.
- Have your soil tested to determine if a low level of potassium, phosphorous or a low pH may be deterring the turfgrass growth.
- Relieve soil compaction by core aerification. This may improve air exchange within the soil and it also disturbs the entangled moss mat and breaks the crust formed by the moss.
Submitted by Kelly Jackson, Agent for Horticulture, Christian County Cooperative Extension Service