Hello David, I don't know much about using ash on the garden. If water is added to the ash it will form an alkaline (caustic) solution of unknown strength. That might burn plants with direct contact. I have put small quantities on incense ash into my compost heap -- diluting it a lot with other stuff, and just sprinkling in a little at a time. There are nutrients in the ash, but it's how to get those out safely onto the plant without damaging your plants or soil biota.

Also depends what is your soil pH? That is, does your soil benefit from liming or is it already alkaline? Acid loving plants like blueberries are definitely not going to want any extra ash. HTH.