Can you put ash in compost

Sprinkling wood ash into a compost heap can be a clever way to recycle fireplace remnants, but it demands care. Wood ash contains calcium carbonate and potassium, which can gently raise pH and supply trace nutrients. However, too much ash turns compost alkaline, slowing microbial breakdown and risking salt buildup.

Before adding ash, ensure it comes solely from untreated hardwood. Coal or painted-wood residues harbour toxic compounds best kept out of garden cycles. For a typical heap, aim for ash to make up no more than five per cent of the total volume. Sprinkle it thinly between layers of green and brown materials, then turn the mix thoroughly to distribute minerals evenly.

If compost will feed acid-loving plants such as blueberries, ericaceous shrubs or potatoes, skip the ash altogether or reserve it for separate batches destined for neutral-ground vegetables and ornamentals. Excess alkalinity can lock up phosphorus and iron, leading to pale leaves and stunted shoots.

When managed thoughtfully, ash-enriched compost lends a subtle boost to borders and vegetable patches alike. It helps deter slugs and snails when scattered around seed beds, too. Ultimately, ash complements traditional organic inputs, creating a balanced, nutrient-rich humus—provided it’s used sparingly and with attention to the needs of each plant.