Using wood ash in your garden

Using wood ash in your garden

We love our wood fire. That big glowing Nectre Mega heater, combined with an air distribution system, keeps our large four bedroom home nice and warm.

The problem with it though, is all that ash. Once a week I grab an old spade and shovel ash and coals into a steel bucket and leave it outside for a few days to cool.

Once cool I usually just throw it in the bin because for years I thought that wood ash was bad for the garden. The truth, like the smoke from the chimney, isn’t quite clear.

Potash is one of those compounds that you’ll find in your local nursery. Adding it to your patch will help your plants become stronger, they’ll resist disease better and taste even finer.

The name potash comes from an old Dutch word ‘Potaschen’. They used to make Potaschen by leaching wood ashes in water and then evaporating the resulting muck in a large metal pot. The white residue was what we now call Potash, or for the scientists amongst us, Potassium carbonate.

Around 10% of wood ash is Potash so sprinkling some on your garden is worthwhile…..too a point.

Wood ash, unlike refined Potash, will raise the alkalinity levels of your soil by a significant amount. This is caused by the large amount of calcium carbonate (about 25%) in the ash. Be warned though that the calcium carbonate works incredibly quickly and will rapidly change your soils ph.

Using wood ash in large amounts will hamper the growth of your acid loving plants like potatoes and blueberries, whilst your slightly acid lovers like your fruit trees won’t appreciate it either,

Vegetables though appreciate a more alkaline soil so some wood ash, around a cup per square metre, will raise the alkalinity, add nutrients like magnesium phosphate and trace amounts of micro-nutrients such as iron, manganese, boron, copper and zinc. and of course the potassium and will save you money. If all you use is compost mixed with a manure like chicken; wood ash will balance out the ph and add some potassium to the soil.

Use Ash on These Plants

  • Lawns
  • Tomatoes
  • Grass
  • Vegetable gardens

Do Not Use Ash on These Acid Loving Plants

  • Potatoes
  • Blueberries
  • Cranberries
  • Rhododendrons
  • Azaleas
  • Magnolias
  • Pine trees
  • Oak trees