Whenever I have a barbecue, or when woody material is burnt, I like to use the cold and dry wood ash to feed around the base of plants in the garden. This is one of the oldest forms of organic feeds in the world, and, along with crushed shells such as Oyster shell, one of the oldest recorded compost mixes used in the UK.
Charcoal can be a useful additive to compost mixes, and is essential when place in the bottom of a container with poor drainage, to keep the compost “sweet”. By this I mean that the charcoal absorbs any unwanted liquids or gasses, such as methane which can harm the plant roots in the container.
The wood ash is also a useful detterent against slugs and snails, who dislike travelling over a soil surface covered in ash. They’re also not too keen on sharp or gritty surfaces, so crushed eggshells or sharp sand (or a combination of both) can help to discourage snails and slugs.
Do remember to keep the garden reasonably tidy and free of leaf litter, especially in the Autumn, when slugs like to hide under leaves. Keeping lawns fairly well edged, particularly when butting up against walls or low edging such as log roll edging, also helps to eradicate suitable hiding places for our slimy eaters of all our precious plants.