Is Roundup Safe on Moss?

Mosses, mushrooms and fungi all enjoy a moist, shady forest environment.


The moist soil under the trees wouldn't grow grass, but at last it's green with a lovely assortment of mosses. Although your shade garden is thriving, a few determined weeds managed to take root amid the layers of velvety green moss. While a glyphosate product such as Roundup is effective against weeds and grass, it doesn't affect moss, making it the best choice for killing the weedy invaders.

How Roundup Works

The main ingredient in Roundup, glyphosate, is absorbed by the weed's leaves and into the sap. Once it is within the sap, it is carried throughout the plant, from the leaves and flowers and down to the roots, killing the entire plant. After the Roundup is completely dry, it is safe to enter the garden and continue your routine chores. The weeds should wilt within hours and die within a few days.

What Roundup Is Used On

Roundup is used on a variety of weeds. Because glyphosate is a nonselective herbicide, it kills both weeds and desirable garden plants. It is not effective, however, on mosses and algaes. Stronger formulations of glyphosate mixed with herbicides, such as triclopyr, provide additional killing action for woody vines and shrubs. The triclopyr helps break through the waxy coating on the leaves, while the glyphosate is carried to the roots, killing the entire vine or shrub.

How to Use Roundup on Weeds

When using a ready-to-use Roundup product, prepare by putting on gloves, safety goggles, long pants, long sleeves and shoes. Choose a clear, windless day with no rain in the forecast. For best results, temperatures should be between 55 and 80 degrees Fahrenheit. Simply spray each actively growing weed with enough Roundup to soak the leaves. If you accidentally spray a desirable plant, immediately soak it with water to wash off the spray, then throw a few shovelfuls of dirt over the leaves to deactivate the Roundup spray.

Maintaining a Moss Garden

Keeping your moss garden green and lush is relatively simple. Mosses prefer a moist environment; water when the soil is dry to the touch to maintain a consistent moisture level. Most native mosses, however, don't need summer watering unless the weather is extremely hot and dry. Mosses also don't need fertilizer to thrive. Avoid pruning too much of the trees' overhead canopy. Keeping the garden cool and shady promotes the growth of moss. Last, avoid walking on the moss.

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