Moss: Beauty or Beast?

Is moss a menace, or a gorgeous green groundcover? Whichever side of the fence you’re on, Carl Grimm from Metro had advice to help you manage your moss without toxic pesticides.

Natural moss is a lush native plant perfectly suited to shady moist areas of Pacific Northwest yards. Visit the Portland Japanese Garden to see how magnificent moss can be. Some love the addition of moss in their home garden while for others it’s an enemy of the perfect lawn. On the roof, moss can shorten the life of your shingles, and on foot paths it can be dangerous. But before you reach for the moss killer, try these tips.

In the lawn: let it be or help your grass smother it naturally
• Let it be. You can embrace the moss! It’s green and needs no mowing.
• Or, if you must have a moss-free lawn, address the root causes of moss: shade, soil compaction, soil acidity and poor soil fertility. These are best handled in fall or spring.
• For reducing shade, prune overhanging branches.
• For reducing compaction, try removing soil plugs with a coring device or rented lawn aerator.
• To physically remove moss, de-thatch with a de-thatching rake or rented power de-thatcher.
• Then over-seed (especially on the thin spots) with an appropriate grass seed.
• Top-dress with a ¼ inch layer of weed-free compost or a mixture of compost and ¼-ten crushed rock. While you’re at it, mix in some slow-release organic fertilizer for fertility and some lime to counteract acidity.
• Unlike moss-killing chemicals, these strategies are long lasting. Plus they won’t stain sidewalks or run into – and pollute – local rivers and streams.

If you want more moss, not less, buy it at your local nursery or blend some up and spread the slurry in the moist spots where you want it to grow.

On the roof: maintenance keeps moss away
• Prune overhanging branches to reduce shading.
• Sweep or hose off the roof once or twice a year to prevent moss growth.
• Remove moss by scrubbing or scraping it off. Asphalt shingles damage easily so be gentle, and avoid pressure-washing since it is very likely to harm the shingles.
• Install zinc strips at regular intervals on the roof. They prevent moss without harmful sprays or powders.
• Metal roofs are great at preventing moss growth. Consider one if you are about to reroof your house. They cost more initially, but last longer and resist moss.
• Be careful! When in doubt about the safety of climbing on your roof, hire a professional.

On sidewalks, driveways and wood: get the moss out without chemicals
• Physical removal by pressure-washing, scraping or scrubbing is the most effective way to keep surfaces moss-free (but don’t pressure-wash the roof – see tips above).
• Chemical moss killers all have issues you may not want to deal with – iron-based products will stain cement and wood. The runoff from soap based moss killers can harm fish in nearby rivers and streams. Zinc granules and powders are hazardous to people and pets.

For more information about moss and more safe and healthy gardening tips, ask Metro by clicking here or call 503-234-3000

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