Buckeye Yard and Garden onLine

Dave Goerig reported an increase in calls relating to moss growing in lawns.  Dave did explain to them that mosses are bryophytes, plants that do not have vascular systems and belong in a division of the plant kingdom that also includes liverworts and hornworts.  One of the most common mosses seen in lawns is from the genus Bryum.  The USDA plants database lists over 60 different species of Bryum. Bryum spp. are not the only  mosses known to colonize lawns; Amblystegium spp. and Brachythecium spp. can usually be discovered on wet and poorly drained soils.

Mosses are opportunistic plants that cannot out-compete a healthy stand of turfgrass.  They usually develop and grow in bare soil areas or where turfgrass is weak and thin.  They can spread rapidly via asexual reproduction or by wind-blown spores. Mowing would seem to spread moss as it involves removing stem cuttings and distributing them to other bare parts of the lawn.  One cultural method for moss control is to keep your lawn healthy.  There are many reasons lawns thin out.  Dense shade, poor drainage, low soil fertility, soil compaction, insect and disease activity, and low soil pH can stress any lawn.  BYGLers all agree that moss encroachment can be minimized where good stands of turfgrass are maintained.

Turf managers and homeowners can combat moss invasions with mechanical methods.  The "roots" of a moss-type plant are called rhizoids. Their primary function is to anchor moss plants to its substrata.  Unfortunately for the moss these structures do not hold the mosses firmly.  To take advantage of this weakness, dethatching is recommended.  Flail type dethatching equipment is available at rental agencies.  Early spring is the best time to control moss using mechanical methods.

Discussion of chemical controls was limited.  Chemical controls on the market are effective, but will not prevent mosses from returning.  The group acknowledged that chemical control without good cultural controls was a waste of time and money.   Most commercial formulations contain iron (Fe), copper (Cu), or zinc (Zn) as active ingredients.  Chelated iron products applied as liquids work well, but the results turn the moss black and stain concrete and other surfaces. Copper and zinc formulations will remove moss on patios and roofs but can injure desirable plants including turf grasses.  Liming the soil to raise the pH may benefit turf, but for the most part, will have no direct effect on the moss.  Cryptocidal soaps are available for moss control and act as contact killers by bleaching the moss foliage.  The golf course industry has sodium carbonate peroxyhydrate (e.g. TerraCyte), and carfentrazone-ethyl (e.g. Quicksilver) labeled for use on moss that is growing on established greens, tees and fairways.  As always, it is illegal to apply these and other plant health products in ways not stated on the label.

For those who can appreciate the natural side of things, consider moss as a ground cover.  Instead of struggling to grow grass, let the moss form a carpet in certain areas of your property, such as under trees or on the Northeast side of the landscape.  Carpets of moss do not require any fertilization, excessive watering or mowing.  Stands of moss carpet can give your landscape a mature and established look.  Moss carpets will not tolerate foot traffic and will require prompt leaf removal in the fall to keep it alive. 

For more information, see:

• Chemical Control of Moss on Putting Greens
• Moss in Lawns
• Controlling Moss in Lawns