Metro Recycling Information
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Choose less-toxic ways to handle the moss in your yard or on your roof or patio.
Mosses are tiny plants that thrive in western Oregon's mild, wet winters. Moss can make a deck or patio slick and dangerous and can damage a roof's shingles, but it also can be a beautiful and carefree ground cover in the garden.
Mosses form a velvety expanse of green in places where grass is not thriving, usually because of excessive shade, poor drainage or overwatering. The simplest solution is to appreciate the moss as a lovely, trouble-free green ground cover that is soft underfoot. But if you’re looking for a solution, read on for ways to prevent moss from growing in your grass.
If you have a shady yard, you may want to try more maintenance-free groundcovers. Native plants that may be useful include Fragaria vesca (woods strawberry), Oxalis oregano (redwood sorrel), or Maianthemum dilatatum (false lily of the valley).
If the moss isn't too extensive, it can be removed manually in early spring.
Rake it out and renovate. Use a dethatching rake or a mechanical dethatcher available from rental agencies. After this procedure, stimulate grass growth and density with organic fertilizer, a topdressing of weed-free compost and locally appropriate grass seed.
Chemical methods are only temporary. Two chemical treatments that will temporarily kill moss in lawns are iron sulfate and potassium soap salts. While both are allowable by national organic standards, they can cause severe skin and eye irritation. The soap salts are also highly toxic to aquatic invertebrates. With either chemical, care is necessary to avoid runoff into storm drains or surface water. These chemicals are short-lived fixes, and still require elbow grease – raking out the dead moss. Unless lawn conditions are improved, the moss will come back.
Problems with roof moss typically arise on north-facing slopes and in the shade. On most standard residential roofing materials – either composition shingles or cedar shingles and shakes – moss can damage the roof.
Leaves and needles hold moisture on the roof's surface and nurture the growth of moss. Maintenance or different roofing materials can prevent problems.
Pressure washing isn't recommended for roofs because the water can get underneath and damage the shingles. In the past, sprinkling detergent to kill the moss was advised. However, roofers now caution against it because the phosphates in detergents were replaced with a degreasing agent that attacks and degrades the asphalt shingles.
Moss can build up on benches, and pose a safety hazard by making surfaces like decks and walkways slippery.
Moss is easiest to remove in the early stages of growth, so the best prevention is regular monitoring and cleaning beginning in the fall.
Scraping and scrubbing removes moss on most surfaces. Pressure washing can make the job easier. While potassium soaps used for lawns can also be used on sidewalks and other structures, runoff can pollute storm drains and surface water.