Bryophyta spp.
moss weedUSDA zones 2–10Active: spring, fall, winterNot a true weed but indicates poor conditions: shade, compaction, low fertility, acidic soil, or excess moisture. Smothers turf in problem areas.
Dense, low, spongy green mat; no true roots, stems, or flowers; thrives in shady, moist, compacted areas.
Moss signals problems: shade, compaction, low pH, poor drainage, or low fertility. Fix the cause, not just the moss.
When: Soil test in spring; address issues year-round
Aerate to reduce compaction, apply lime to raise pH if soil test indicates acidity.
When: Aerate in fall; apply lime per soil test recommendations
Dissolve baking soda in water and spray on moss patches. Raises local pH to discourage moss.
When: Apply in spring when moss is actively growing
Turns moss black within hours. Also feeds the lawn as an iron supplement. Safest chemical option.
When: Apply in spring to actively growing moss; rake out dead moss after 2 weeks
Active ingredient: Ferrous sulfate — e.g. Moss Out, Lilly Miller Moss Out
Grass safety: always match herbicides to your grass species — products safe on Kentucky bluegrass can kill St. Augustine or centipede. Lawn Guardian checks this automatically against your lawn profile.
Lawn Guardian turns this guidance into a schedule timed to your USDA zone and this week's actual weather — and adapts every time you log what you've done.
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