What Kills Weeds but Not Moss?

Moss gardens are a practical and water-saving alternative to the traditional grass lawn. Mosses are non-vascular plants that acquire much of their energy and moisture from the air. They are easy to grow and infrequently become weedy and need treatment. In case of weed problems, systemic and pre-emergence treatments can be helpful without harming your green mossy area.

Mosses are very simple plants that are extremely tolerant of different conditions and grow in most locations of the world. There are thousands of species of moss with very different leaf, shoot, root and seed-forming mechanisms than other plants. Mosses spread through spores and also be can reproduced vegetatively by breaking off pieces. They often are found in poorly drained, compacted soil with dubious fertility and medium to dense shade, areas that are not usually prone to weeds.

Systemic herbicides have little detrimental effect on moss. This is because moss does not have a vascular system that brings nutrients and water in through roots and into the various parts of the plant. Instead, mosses can get most of their moisture and food needs from the air. Systemic herbicides work by traveling through the roots and vascular system of a weed. They have proven to be useful controlling weeds without harming the mosses. Any herbicide with glyphosate as the active ingredient is appropriate for weed control in moss gardens.

Moss transplants easily, requiring supplemental moisture until it establishes. Moss also can be grown through a moss milkshake or slurry. Each little piece of moss has the ability to grow a complete new plant in the right conditions. The slurry is a mixture of buttermilk, corn syrup, beer and chopped up moss. Make certain to treat the area with a pre-emergent herbicide before you pour the slurry. This will help minimize future weed competition as your moss area becomes established. Moss grows slowly so it may take several seasons to grow a sizable patch.

A thick, well-established carpet of moss has few weed problems. Because moss prefers shade, weeds do not tend to grow in large numbers where they do not get sunlight. This means fewer, if any, weed problems. A product with the active ingredient trifluralin has been shown to be safe in patch areas of moss. It doesn't kill actively growing plants but prevents weed seeds from germinating. You can apply it in spring before weeds germinate and use a spot spray treatment of glyphosate as problem weeds pop up.