Does lime kill moss?
No, lime does not kill moss. It helps the grass on acid soil.
Calcium carbonate is not toxic to moss. Moss moves in where grass is weak: shade, wet or compacted ground, short mowing, hunger, or acid soil. Lime fixes only the last of those, so test first. Below pH 5.5, lime helps the grass grow thicker, lifting the soil towards 6.0, the UK target for grassland (Goulding, 2016).
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- Lime raises pH; it does not kill moss. Most moss killers are iron sulphate, which acidifies.
- Lime only where a test reads below pH 5.5.
- Rake the moss out, then fix whatever let it in.
Why the moss is there
| Cause | Sign | Fix |
|---|---|---|
| Acid soil | pH test below 5.5 | Lime in autumn or early spring |
| Shade | Moss under trees and on the shady side | Lift the canopy; overseed with shade-tolerant grass |
| Wet or compacted ground | Puddles; hard soil | Spike or hollow-tine in autumn |
| Hungry grass | Thin, pale lawn | Feed in spring and autumn |
| Mowing too short | Scalped patches | Raise the blades; take off no more than a third |
Work out your exact amount. Enter your area, your test reading and your soil type, and the calculator gives the dose, the timing and the bags to buy.
If the test says lime
- 225 to 300 g per m² per half pH unit. Sand at the low end, clay at the top, spread on the surface. Never more than about 400 g per m² in one go; split bigger amounts between autumn and spring. Full table in lime for lawns.
- Autumn or early spring. On a dry day, then water in or let rain do it. Not on frozen or waterlogged grass.
- Not with iron sulphate or feed. Leave about a month between them.
Common questions
Should I lime before or after killing moss?
Deal with the moss first, then lime a month later if the test shows acid soil. Do not put lime and iron sulphate down together.
Will lime get rid of moss?
No. On acid soil it helps the grass grow thicker; on neutral soil it does nothing. Moss still has to be raked out, and shade, drainage, feeding and mowing matter as much.
Can too much lime harm a lawn?
Yes. Above about pH 7.5, grass takes up iron and manganese less well, and it is slow to reverse. That is why you test first.
Is garden lime safe for pets?
Calcium carbonate is the mineral in chalk and limestone. At these rates it is safe around children and pets; keep them off until it has been watered in.
When should I lime a lawn?
Autumn or early spring, on a dry day, and only after a test reads below 5.5. Keep it a month away from feed and moss killer. See lime for lawns.
More: Granulated Lime · soil pH calculator · lime for lawns · how to test soil pH · acidic soil · iron sulphate vs sulphur · lawn care
Fine lime that goes through a spreader
About 98% calcium carbonate in 2 to 5 mm granules that fall back to flour when wet. Lime to a test, never by habit.
Buy the size for your area
Free UK delivery over £40. Buy now goes straight to checkout.
Free UK delivery over £40. Dispatched in 1 to 2 working days. Packed and posted from Stockport.