Alan Gould wrote:

In article , HaaRoy
writes
I have always thought that using ash from the bonfire was good for the
plants but am i under a false illusion ?

No, garden bonfire ash from mainly brushwood and similar material makes
a good potash based plant dressing, it is especially beneficial to soft
fruit bushes. The ash should be allowed to mature for several weeks,

Potash is very water soluble. This will mainly result in the area under
your ash heap getting an excess. It quickly leaches out every time it
rains. Fruit trees and soft fruit can take it when dormant and it
discourages the grass under them if applied fresh. It can burn leaves
though if they are actively growing.

I find onions quite like the extra drainage that the rough charcoal from
the embers provides. YMMV

Applied at this time of year (or preferably a bit earlier) it encourages
next seasons flowering.

longer if you can, then diluted with ordinary soil sifted fine, or a
little sharp sand. It should not be applied directly touching the stems
of plants. Bonfire ash can also be dusted onto compost heaps, or used
sparingly in conjunction with mulches.

Coal or smokeless fuel ash cannot be recommended for garden use at least if
you intend to eat the produce. There are too many heavy metal impurities in
the resulting ash to use on the veg plot.

Regards,
Martin Brown