You can use fireplace ash in your garden, but use it sparingly. Central Coast soils tend to be slightly alkaline. Our water is also slightly alkaline (pH 7.2 to 7.5). Ideal soil pH for growing most plants is 6 to 7. Wood ashes are also alkaline, having a pH as high as 8-9. High soil pH causes some nutrients to become less available to plants. Therefore, adding wood ash can aggravate plant nutrient availability, rather than help. Do not use wood ash to amend soil around azaleas, rhododendrons, camellias, gardenias, citrus, apples, blueberries, and other plants that must have acidic soil conditions in order to grow.
