TL;DR
Iron sulphate for lawns. Zinc for roofs and hard surfaces. Never swap them. Zinc damages grass and iron sulphate is ineffective on roofs.
If you’ve been researching moss removal you’ve probably come across both iron sulphate and zinc as solutions. They both kill moss but they are not interchangeable and using the wrong one in the wrong place is a common and costly mistake.
Iron Sulphate: For Lawns
Iron sulphate is the right choice for moss growing in your lawn. Look for it listed on product labels as ferrous sulphate, ferric sulphate, ferrous ammonium sulphate, or iron-based moss control. These are all the same family of product and widely available at hardware stores across BC.
It kills lawn moss effectively without damaging your grass. Apply, wait 1-2 weeks for the moss to die and turn black, then dethatch and reseed the bare patches.
Do not use zinc powder on your lawn. It will damage your grass.
Zinc: For Roofs and Hard Surfaces
Zinc powder is the right choice for moss on asphalt shingle roofs. Applied along the ridge line it washes down slowly with BC’s rainfall creating an environment where moss cannot establish. It is a preventative treatment as much as a removal tool.
It is not suitable for lawns. Keep it strictly for roof and exterior hard surface applications.
The Simple Rule
- Moss on your lawn: iron sulphate
- Moss on your roof: zinc powder
- Never swap them
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