i wishuse of wood ash in the soil

If its black and burnt there's no problem with pathogens and invisible nasties. However, it will more than likely behave like sand and serve to clog up your soil...

Wood ash is particulary good for root vegetables but don't use too much. A sprinkling over the soil is all that should be needed. As Muddy says, too much will clog up the pores in the soil when it gets damp.Also make sure that it is pure woodash. If you have been burning coal as well then this will c onain sulphur which is not good.

spot on Bulbaholic ' there is nothing I can add,

is it good for cammelia's ?

Wood ash is potash and is of most use for building up good, strong roots. Used lightly, most plants would benefit from it.

As we have wood central heating via a kitchen stove/cooker and several wood stoves, we have built up a huge pile of ash over the last couple of years. I read it might be good for cane fruit, such as raspberries, but I'm not sure how much to use, or when to put it over the soil.

Bertie, unless there is a deficit of some nutrient in the soil all plants get most benefit from a balanced feed. On the other hand there is rarely any problem in giving a small amount of something as a special treat. The wood ash will help with the general vigour of the raspberries but don't overdo it. Stand upwind of the canes and sprinkle a few handfuls over the roots.
Like me, you will have far more wood ash than the garden will take. I suppose that we could start a business producing bleach?
Thinking laterally as I write, they did use to make bleach for the cotton mills from woodash by soaking it in water. This is probably a good reason to only apply wood ash lightly to the soil as too much could possibly be turned into a caustic by the rain! Could it? I don't really know, I'm just rabbiting away.

Bulbaholic can you go a bit further for me please - why do forest regrow so well after fires (I know some seeds need heat to regenerate) but in all that ash?
Part of my garden is on an old coal yard (for over 100 years) often dig up coal (I have had to add a lot of humas to try to get some water retention) should I be nuetralising this part of the garden if it has sulpher due to the coal?

Lumps of coal are like stones and the sulphur is bound up. When the coal is burned the sulphur is released into the ash and so becomes available to the environment.
Don't read too much into the last paragraph of my previous answere to Bertie. This was just an idea going through my mind (it works like that) as I was wrtiting.

Thanks

Dcr I've often wondered how forests grow from ashes. Also I've been told that leaf mould hasn't much goodness and is only useful as a conditioner. So why do trees grow so well without extra food.

me too Heron!

Heron wonders why trees grow so well without extra food, but you have only to walk through a wood to see that the majority of trees don't grow very well. There are far more stunted, twisted, and dying trees than healthy ones. It's the survival of the fittest and just a few super specimens with good roots and a bit more light get to make it. They also say that all the fertility in the tropical rain forest is in the top few centimetres of soil so that once it's chopped down they only get one or two good crops from the land before it turns to desert.
Having said all that, I too am intrigued how you can plant a well grown tree from a pot into poor soil which never grows properly, while a few inches away a naturally seed grown specimen shoots off to make eventually a huge healthy deep rooted tree. I'm just looking at all the oak trees which have come up naturally in our field and are shooting up (relatively speaking for oak trees), while the other trees I planted are hardly surviving.