Wood Ash
Ash from untreated wood that supplies potassium and calcium, raises soil pH, and doubles as a physical deterrent against slugs and snails.
What it is
Wood ash is the residue left after burning dry, untreated hardwood or softwood. It is approved for organic production and contains significant amounts of potassium carbonate and calcium carbonate (lime equivalent), along with a range of trace minerals. Its potassium content ranges from 3 - 8% and its lime equivalent from 25 - 50% depending on the wood species.
What it does
Wood ash raises soil pH through its alkaline calcium and potassium carbonate content, making it useful for correcting acidic soils and improving brassica beds prone to clubroot. Potassium from ash improves fruit quality, cold hardiness, and disease resistance. When applied as a dry surface barrier, the abrasive, alkaline particles deter slugs and snails through direct physical and chemical irritation.
When to use
Apply to soil in spring before planting at no more than 4-6 oz per square yard. Use on acid soils that would benefit from raised pH, or on brassica beds as a seasonal clubroot deterrent. As a slug barrier, apply a dry ring around vulnerable plants and reapply after rain. Particularly valuable on potassium-hungry crops such as tomatoes, potatoes, and beans.
When not to use
Do not apply wood ash to alkaline soils (pH above 7) or around acid-loving plants such as blueberries, rhododendrons, and camellias. Avoid mixing directly with fresh manure or nitrogen fertilisers as the alkalinity promotes ammonia loss. Never use ash from treated wood, painted wood, coal, or charcoal as these may contain toxic residues.
How to apply
- 1
Allow ash to cool completely and store dry in a sealed container until ready to use.
- 2
For soil application, scatter thinly and evenly at 4-6 oz per square yard over the bed surface. Avoid heavy concentrations around the base of plants.
- 3
Rake or lightly fork the ash into the top few inches of soil to prevent it blowing and to begin incorporation.
- 4
For slug and snail barriers, create a dry ring 2 inches wide around vulnerable transplants. Reapply after each rain event.
- 5
Water the bed after incorporation to begin releasing the potassium and lime into the soil profile.
Used for
Garden, by Willowbottom recommends only organic, wildlife-friendly solutions. No synthetic pesticides, no harmful chemicals - ever.