7 Ways to use Wood Ash in Your Garden

As well as 7 ways to use wood ash in your garden, we’ll look at what wood ash is, the types you shouldn’t use and how to store it.

Wood ash is quite simply the residue remaining in the hearth and ash pan beneath your open fire or log burning stove. It may also be the ash remaining after your bonfire, whether that’s for Gur Fawkes Night or clearing up garden waste. This latter may have had, for example, dead brambles and small twigs in the mix but it is still useable. Although the focus is on ash from your indoor fire or stove, charcoal and logs burnt in a firepit or BBQ may also be suitable.

Let’s recap the possible sources of your wood ash –

An open fire
Log burning stove
Range cooker
Garden bonfire
BBQ
Firepit

Some of these sources will only give you occasional buckets of wood ash, others may give you a constant supply. And especially with the increase in use of log burning stoves, more people are finding they have buckets full of wood ash. Indeed, if your neighbour has a wood burning stove but isn’t a gardener, you may be able to relieve then of the ash and prevent it from going to landfill.

Which wood ash should you NOT use?

Its not a long list! By the way this is not about the types of wood to burn – I’ll put that in another blog and suggest ways of growing at least some of your wood supply even in an average sized garden.

Treated wood –

Which is for example, decking boards and fencing, as this will have been treated with preservatives to improve its longevity as building structure. Which means that the ash may contain potentially harmful residues. Personally, I don’t burn this timber in the first place, taking it to be recycled instead. That way I can’t get my ‘good’ and ‘bad’ ash muddled up!

Painted wood –

Painted, sealed or stained wood is likely to have the same issues with potentially harmful residues.

Old railway sleepers –

These will have soaked up oil, tar and goodness knows what else over the years.

Wood that has been burnt with other materials –

This one is obvious, and may be relevant if it’s from a communal Fireworks Night bonfire, for example. What you want is wood ash, not bits of plastic or worse.

Charcoal –

If you’ve used lumpwood charcoal, then the ash from that is fine. But ash from charcoal briquettes should not be used.

Ways to use Wood Ash in Your Garden

Historically wood ash has been used for centuries both in the garden and in the home, as a soil improver and fertiliser and as a cleaning agent. If you want to be more self-sufficient, you may even like to try your hand at making lye soap (See blog link below). But for most of us, simpler uses for wood ash around the garden are in order.

The tree type and species that was burnt as wood will produce wood ash with different nutrient levels. Hardwoods are broad leaved tree species, both deciduous, oak for example, and evergreen, such as laurel. These have higher levels of nutrients and minerals than the softwoods, which are conifers.

The proportion of potassium found in wood ash will also vary according to the age of the timber. Young wood such as that from pruning a tree will have higher potassium content than older, thicker branches. Potassium and potash are not identical substances, but are frequently used as interchangeable terms by many gardeners and non-scientists.

Although wood ash contains zinc and manganese, the main elements we’re interested in are potassium (potash) and calcium carbonate (lime).

Potassium forms one part of the general garden fertilisers which contain the three major plant nutrients. NPK, or Nitrogen, Phosphorous and Potassium needed for healthy plant growth. Potassium is particularly important in the formation of fruits and flowers.

7 Ways to use Wood Ash in Your Garden

See safety notes below before using.

Soil

Applying wood ash directly to soils is best done in in winter as this will allow the compounds in the ash which could scorch plants to react with the moist soil and be rendered harmless before spring sowing or planting. As a minimum, apply it at least a month before planting.

Wood ash can be spread directly on soil in the vegetable garden in late winter at a rate of 50-70g per sq m (1.7-2.4oz per sq yd). Fork or rake it in, or rotovate.

Dust baths for wild birds and domestic hens

Place cold ashes in a dip in the hen run where your chickens can get to them and the dust baths will help control mites. The birds that visit your garden will also relish a dust bath in wood ashes as they too suffer from mites and bugs.

Pest deterrent

Spread a ring around individual plants that slugs and snails find especially tasty. They’re not keen on crossing over the dry, salty substance of wood ash.

Try sprinkling wood ash into the drills when you sow your carrots, as it should help to keep carrot turnip fly away.

Are you plagued by ants’ nests? You could throw some wood ash into their colony. They will be forced to relocate, as they can’t move the ash. (Although I can’t promise they won’t just up sticks to another part of your garden or vegetable plot!

Wood Ash and the Compost heap

Possibly the easiest of our 7 ways to use wood ash in your garden.

It’s best to apply wood ash to the compost heap in small amounts and mix it in, so that it blends easily with other materials. This lessens its effect on the pH of the compost, the busy worms and friendly compost bacteria. As a general guide, you should not be able to identify it after mixing it into the compost.

If you compost a lot of acidic material, such as fruit waste, the wood ash will help to keep the compost at a more neutral pH. Which makes it useable on a wider range of plants.

Lawn Fertiliser

Wood ash contains 10-25% calcium, 1-4% magnesium, 5-15% potassium and 1-3% phosphorus. So it makes a good spring fertiliser for your lawn. You could store it over the winter months, being sure to keep it dry, so that come the spring you have enough to fertilise your whole lawn.

Snow and Ice melting

The salt in the alkaline wood ash makes it a good substance to throw on frosty paths. Use as an ice melt and for traction on icy paths and driveways. Wood ash is safe for pets and any bordering grass or plants too, unlike rock salt.

As a Lime Alternative in the Vegetable Garden

One of the benefits of using wood ash instead of lime is that it acts faster. You should see the results from wood ash within in a month. Remember to take a pH test before adding lime and after a month. It’s okay to add a second application of wood ash if the pH is still not high enough.

Brassicas including cauliflower, broccoli, and Brussels sprouts appreciate a higher pH as it helps to prevent clubroot.

But avoid using wood ash on areas where potatoes are to be grown the following spring, as the alkaline conditions can encourage potato scab.

7 Ways to use Wood Ash in Your Garden – Safety Notes

For you –

Make sure that the ash you are spreading is well cooled and is no longer burning. Be aware that when ash is piled or bucketed when still hot ,the inner layers can hold heat and smoulder for quite some time—days even.
It may be useful to sieve the ash before use to remove debris and larger pieces..
Wood ash can be irritating to the eyes, nose, respiratory tract, and to bare skin. Avoid breathing in the dust by using a face protection and limit skin exposure by wearing gloves, boots and work clothes

For your garden –

It is a good idea to use a pH test kit to take a base line reading before first applying the wood ash. Check regularly to monitor changes in pH levels, as higher pH 7.5 is detrimental for a great many plants.
Spread wood ash evenly and do not leave large clumps or piles which can result in too many salts concentrating in one area. Up to a half inch of ash is fine.
When used as soil improver, heavy clay soils can take more wood ash than sandy soils.

And finally…

7 ways to use wood ash in your garden wouldn’t be complete without telling you how to store the ash whilst it cools and for the longer term.

The ash should be kept dry and out of the weather as beneficial salts and nutrients will leach out of the ash with rain, snow melt and water. Storing it in a metal container with a cover is usually the best method. For example, a galvanized metal bin, which can be found in various sizes.

NB Make sure that the ash has cooled and is no longer burning, before covering and storing!

Free for You

We’re always adding to our freebie gardening printables for you to download. These include plant lists to inspire you, planners to help with your gardening tasks. (We’re moving things around, so you may find some of them at the bottom of the eBooks here

For further gardening advice and inspiration, check out Plews Potting Shed blogs, including the winter gardening tips and ideas selection below and our monthly Tipsheet

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