Is Roundup Safe on Moss?

Mosses

• Mosses are fairly simple forms of plant life but have very clever survival characteristics. Mosses thrive in slightly acidic soils and can grow on surfaces without the usual level of soil such as rocks or cement. Moss grows on compacted soils and inhospitable terrain as long as it is in shade or partial shade with even levels of moisture. Moss is propagated from spores that travel in water or air. It can reproduce vegetatively by breaking off pieces that regrow.

Glyphosate

• Glyphosate is a broad spectrum, non-selective herbicide that is widely used for a variety of weed control. The chemical is used in the Roundup brand chemical herbicides among others. It is absorbed through a plant's leaves or soft stalks and invades the vascular system and inhibits amino acid metabolism. Over time the plant dies completely and is not just top killed because the herbicide travels to all parts of the plant. In mosses the ability to circulate through the entire plant is prevented by the lack of a vascular system, which keeps the chemical from killing the moss.

Glyphosate on Moss

• Many homeowners do not want to have to manage the high maintenance needs of traditional sod lawns. Moss grows quickly and fills in fast, the growth is dense enough to repel most weeds, it needs no fertilizer and it is cheap, which makes it an ideal replacement for a traditional sod lawn. Occasionally weeds will penetrate the lush growth and the weeds entangle with the moss making weeds difficult to remove. Glyphosate is safe to use on all but the most leafy types of moss. The chemical penetrates the plant through the leaves and travels through the vascular system so mosses are unaffected because they have no vascular system.

Use

• Weeds are a bigger problem on mosses that are newly planted or just getting established. Over time they fill in and become thick enough to prevent most weeds from growing among them. Glyphosate is useful as a pre-emergent herbicide before planting a moss garden. It will prevent any existing annual weeds from sprouting. Spot treatments of a half dilution of glyphosate with water can be useful in treating perennial and broadleaf weeds. The chemical may discolor the moss but the moss will turn green again in time.