What to do with wood ash?

Winter is well and truly here. Many of us, in order to avoid boosting our contribution to load shedding, will have oil, gas or wood heaters.

During these dark nights, nothing is nicer than the sight of a lovely wood fire.

Environmental considerations aside (although burning wood is better than dumping it!), the ritual of removing the ash from the fireplace/stove in the morning quickly becomes a winter ritual.

But what to do with this ash? Do not add it to your dustbin. Wood ash is full of wonderful nutrients which can boost the health of your soil.

While the minerals in wood ash will differ according to the (invader) species burnt, the major constituent is calcium carbonate (the basis for the making of potash). Wood ash is thus alkali (high pH) and is a wonderful input for raising the pH of acidic soil; it is a nutrient rich alternative to agricultural lime. When substituting wood ash for lime double the application rate.

Wood ash contains important trace elements including phosphorous, potassium, calcium, boron and other elements healthy plants need. While nitrogen and sulphur have been burnt off the remaining PK elements of the NPK value are key to plant health and development. Phosphorous (P) is important for root and foliage growth including fruit development. Potassium (K) is an overall plant health booster.

Ash, especially that from hard woods, has high calcium content. Calcium is a mineral which is often missing from our soil. Calcium is used by plants when building their molecular and cell structures. Added to soil, wood ash is able to replenish the calcium taken up by plants and can be used as a substitute for bone meal when planting alkaline loving trees or shrubs.

In a forest trees feed themselves through dropping leaves and twigs in the winter. This material converts back to humus which is taken up by the soil in order to reinvigorate the tree in the spring growing season. Wood ash replaces the soil minerals trees have, mined, during their growth season.

Wood ash is also great for compost. Not only will it help neutralise the pH of your compost it also adds key mineral nutrients to the matrix. A pH neutral compost heap is an ideal environment for composting microorganisms; adding wood ash can thus help turn your garden greens into compost quicker.

The salts in wood ash are also excellent for controlling or killing snails and slugs; a much better alternative to snail baits which, deadly effective, have a wider detrimental effect on your soil and the wildlife living in and visiting your garden.

A note of caution, many of plants prefer acidic soil (lower pH); do not use wood ash around these acid loving plants. Never simply pile up your ash on your soil or around a plant as this will concentrate their salts in one place. It is better to spread the ash out thinly across a larger area. Do not use wood ash on seedlings; the salt content is too high for these plants at this vulnerable stage of their development.

Wood ash should only come from untreated natural wood. The chemical residues from treated wood ash will have a detrimental effect on the soil.

at type of wood burner should you be looking for? An efficient wood burning stove will leave very little residual charcoal. If you’re thinking of purchasing a wood burning stove look for the Double Burner type. These are very efficient and also burn the wood gases emitted during combustion.

If you already have a nice fireplace you will always have some left over charcoal bits. Use these for your next burn or add this to your soil. This charcoal adds useful carbon to your soil and helps with building the soil-food-web while also helping with water retention and the overall tilth.

Whichever way you decide to recycle your wood ash, keep warm this winter. Enjoy a lovely vegetable soup. Cuddle up. Enjoy the rest of Game of Thrones. Winter is Coming.

(t) +27 11 959 1083

This website uses cookies to optimise your browsing experience. Please check out our Privacy Policy for more information.