Unwanted moss

Asked November 27, 2019, 4:55 PM EST

What is the best way to get rid of moss in dirt and flower beds and keep it gone? I live in Washington state and our yard is mostly shady with many fir trees. Can I use a lawn moss killer with nitrogen and iron? Should I be using a pre-emergent like Caseron? The moss is also invading our lawn even after we had it professionally killed, thatched and reseeded. How do I get the soil tested for pH? I’m thinking I need to add lime to raise the pH from all the acidic fir needles over the years.

King County Washington

1 Response

Hi—Yep—moss in lawns can be a real problem up here in the PNW. So here are the recommendations from WSU—Moss usually grows in areas where the soil fertility is low, the acidity is high, where the soil is poorly drained and/or compacted, or not watered properly during the summer months. So the first thing to do is to PREVENT it—which you’ll want to do once you fix the problem. Maintain a healthy, vigorously growing lawn by irrigating, fertilizing, and cutting it properly. Take steps to make sure your lawn has good drainage. Hand –raking to remove the moss will also help to control it. And I can’t stress this last one enough: Get a soil test. We’ve been recommending Simply Soil testing (http://www.simplysoiltesting.com/Services.html--order the S5 test $24) OR A&L Western Laboratories http://www.al-labs-west.com/fee-schedule.php?section=Soil%20 Analysis Sc3 with recommendations $35). You will save money by knowing exactly what you need to do to correct soil problems, instead of buying and trying things that don’t work.

Here are a couple of good publications for taking care of your lawn:

https://www.seattle.gov/Documents/Departments/SPU/EnvironmentConservation/NaturalLawnCare.pdf https://www.co.thurston.wa.us/health/ehcsg/pdf/lawn_care.pdf

Now to try to take care of the immediate problem. Fall, winter and spring, when the moss is growing vigorously, is the best time to treat it. Here are some options to try. Remember to read all instructions and follow them closely:

  • Lilly Miller Moss-Out! For Lawns Active ingredient: ferrous sulfate | EPA reg no: 802-509
  • Scotts Turf Builder with Moss Control 22-2-2 Active ingredient: ferrous sulfate monohydrate | EPA reg no: 538-223

This list may not include all products registered for this use.