Wood ash contains potassium and other trace elements which are beneficial to plants. You can use it just about anywhere in the garden, especially for vegetables. Dig it well into the soil during winter or add it to your compost heap in small quantities every now and again. Be careful that you don't add too much to the soil as this will alter the pH balance of the soil causing it to become too alkaline which will have a detrimental effect on some acid loving plants. Having said that, it would be a good thing to add instead of lime to balance out an acid soil.

I would leave it until spring before you apply it though potash is very highly soluble and may get washed out of the soil before next growing season. It encourages fruits and flowers so this will be a guide as to which plants to put it on. Not on raspberries though.

Great, thank you for the advice.