A treated lawn gathers less moss

Due to our seasonal weather patterns (rain and more rain plus rain), lawn moss is a permanent fixture here in the Pacific Northwest. Moss germinates from spores cast from the adult plants as they mature. If wet conditions prevail, those spores will germinate, and new moss plants can begin to grow almost immediately, even after being treated.

Ferrous sulfate (iron):

Ferrous sulfate is the active ingredient in many moss killers you might find on the shelves of home and garden stores. These products are registered for homeowner use and would be prohibitively expensive to use in the professional lawn care industry.

We add ferrous sulfate to our fertilizer mixes all year, to promote color and chlorophyll production in your lawn. If applied at a high rate, as we do in Winter and Spring, ferrous sulfate will damage moss. After high-iron fertilizer applications, the visible moss plants turn dark and begin to shrink in size. But, even at high rates, ferrous sulfate won’t permanently eradicate moss, nor should we expect it to. Like death and taxes, as the saying goes, moss will always be around.

Mechanical removal:

Mechanical removal, by hand raking or with a dethatching machine, is a quick (and by far, the most fun!) way to eliminate most of the existing lawn moss. However, moss will grow back. Maintaining healthy turf and soil with proper fertilizer, irrigation, aerating and over-seeding (more grass plants, less room for moss) will help keep moss out of the lawn. In shady areas, over-seeding should be done annually. Our office has referrals for great companies who provide aeration and over-seeding service.


Contrary to what you may have heard, lime will not control or prevent lawn moss. Prescription lime applications will correct acidic soil, improve the ability of grass plants to assimilate nutrients through their roots and perform better. We do NOT recommend liming your lawn without a current pH test showing the need. We can test for you if you don’t have a current reading.


The bottom line is: you can expect to see lawn moss Fall through Spring, especially if your lawn is thin, shady, or poorly drained, and even more so during years of frequent rainfall and cool temperatures. High iron fertilizer programs help minimize the accumulation of moss, but we cannot expect moss to disappear forever; it’s just not going to happen.