Wood ash from fires, log burners or stoves and garden bonfires is a problem, or a bonus. It depends on your viewpoint. A problem if it fills your waste bin. Recycle it in your garden and wood ash turns into a bonus!

wood ash

Wood ash from log burners and bonfires - a free bonus plant food.

Why is wood ash a bonus for my garden?

It contains potassium which supports healthy and strong growth, flowers and fruit.  Younger wood contains more potassium than older wood, so ash from a garden bonfire where this year’s (over)growth and prunings were burned is likely to be a plant superfood.

Sprinkled on, and loosely forked into the soil, wood ash can reduce soil acidity which many plants appreciate. Mixed into garden compost it makes an alkaline compost good for plants that don’t like acidic soils.

If you grow leafy green veg. and have suffered from ‘club root’, wood ash is what you need because it can raise the pH to 7.5 and that can inhibit the disease.

And it's free!

So, what do I do to make the most of wood ash?

Sprinkle a shovel full onto compost heaps and mix it in. This is a MUST do if your compost heap (like mine) is mainly waste from fruit and veg. mixed with grass cuttings. Why? Because the mix is likely to be too acid to support the little red worms that do such a good job turning waste into goodness for your soil and adding wood ash will make it less acid.


wood ash

Fork wood ash lightly into the soil through the winter (the RHS recommends at a rate of 50-70g per sq m (1.7-2.4oz per sq yd) and roughly fork it in. Or sprinkle on the soil around plants that are showing yellow and brown edges to their leaves, because this often indicates a shortage of potassium which the ash can rectify.  Sarah Buchanan.

Great, is there anything I should not do with wood ash?

Yes! Don't:

  • add to the soil around acid loving plants such as rhododendrons, azalea, raspberries and roses
  • add to soil with a pH of 7.0 or more.
  • leave piles out in the rain; the rain will wash the potassium out and all is lost. If you can't sprinkle it where you want it before rain,  store the wood ash in a dry place
  • use wood ash from ‘treated’ timber, such as old fences, or from briquettes used on barbecues as these may contain elements that are not good for the soil.

And what is all this about garden bonfires? I can't have one!

Ah yes - the smoke from garden bonfires means they are not on in many built up areas, in small gardens and in gardens close to busy roads. If your community has a playing field bonfire in the autumn or winter, or local allotments allow bonfires, find out if you can add your prunings to the fire and share in the ash.