Posted: 07/04/2013 at 13:32
Wood ash is good for use around the garden but avoid using it on any plants which prefer acid conditions as it is alkaline. I would advise against using the briquette ash though as it may contain traces of heavy metals which are not good for plants or animals, including us.
Plants to avoid using the wood ash on include (but are not limited to): Acer, Azalea, Camelia, Heather, Rhododendron, Blueberry, Cranberry, Raspberry, Apple, Grape, Strawberry, Potato. If you aren't sure about a particular plant, use google and search for the plant name and add "growing conditions" to see if it prefers acid soil (pH lower than 6.5) - if so, avoid using the wood ash on it.