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Use wood ash correctly

Ash from clean firewood contains potassium and calcium and acts like fast lime. Used wrongly it can push soil too alkaline or harm plants.

How

1. Test your soil pH first. Do not apply ash if soil pH is already above 7.0.
2. Apply no more than about 20 lb per 1,000 sq ft per year (about 1 kg per 10 m2), in winter or early spring on a calm day, worked into the top few centimetres.
3. Treat ash as roughly half as strong as garden lime when following a soil test (its calcium carbonate equivalent is about 25 to 59%).
4. Keep it away from blueberries, azaleas, rhododendrons and potato beds (higher pH increases potato scab), and away from germinating seeds.
5. Never mix ash with urea or ammonium fertilisers: ammonia gas can be released.
6. Only use ash from clean, untreated wood, never from painted or treated wood or burned rubbish. Keep it under 5% of compost volume and store it dry in a lidded container.
7. Store stove ash in a metal container with a lid, outdoors and at least 10 ft (3 m) from the house, as the US Fire Administration advises, until it is fully cold.

Safety: Ash is caustic: wear gloves, long sleeves, eye protection and a dust mask. Ash from a stove can stay hot; see the safety module for storage.

Do these first

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Sources

1. Using Wood Ashes in the Home Garden. Iowa State University Extension and Outreach, accessed 2026-11
2. Fireplace and Wood Stove Safety Card. US Fire Administration (FEMA), accessed 2026-11

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