How to Use Wood Ash in the Vegetable Garden

Benefits of Wood Ash in the Garden

January 10, 2019

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If you have a fireplace or woodstove, use wood ashes to improve garden soil! Wood ash is full of nutrients that plants need, such as potassium and phosphorus, so it’s great for using on the vegetable garden. But it’s important to know where not to use it, too. In this short video, we show you when, where and how much wood ash to apply to keep your plants in tiptop condition.

Wood ash is particularly useful for fruiting plants.

Ash from hardwoods like oak and beech are best as they contain more nutrients than ashes of softwoods like pine. Avoid using the ash from coal or treated timber, which could be harmful to your soil and plants. 

The nutrients in wood ash are soluble. They must be kept out of the rain so they don’t wash out. Use a container with a close-fitting lid to keep your wood ash dry until you’re ready to use it. 

Composting Wood Ash

Wood ash is alkaline, so it can help to reduce the acidity of a compost heap. This creates better conditions for composting worms and results in compost that is perfect for mulching around vegetables. 

Add thin layers of wood ash to your compost heap no more frequently than every six inches of material.

Using Wood Ash on Garden Soil

Most vegetables need a pH of 6.5 to 7.0. If your soil’s below 6.5, fork or rake wood ash to help raise the pH. You can test your soil using an inexpensive test kit to find out its pH. 

Wood ash is about half as effective as lime in neutralizing acid. As a general rule, scatter about two ounces of ash to every square yard. Do this on a still day in winter and wear gloves to protect your hands. 

Brassicas such as cabbage and Brussels sprouts are best grown in a more alkaline soil. Apply wood ash the winter before planting, or around actively growing plants. 

Wood ash is high in potassium, which helps flowering and fruiting, so it’s ideal to use around most fruit bushes and around fruiting vegetables such as tomatoes. 

Avoid using wood ash around plants that require an acid soil such as blueberries. Don’t let it come into contact with seedlings or use on potato beds, as alkaline soil encourages potato scab.

Wood ash would need to be used in huge quantities to make your soil too alkaline for most other crops, but it would be worth re-testing your soil’s pH every two years to check it doesn’t go above 7.5. 

See MORE ways to use wood ashes in the home and garden.

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Wood ash from fireplace

I use my ashes from the fireplace every year to put under my bushes and some trees. Since my soil is very acidic from the many pines in the yard, I think the ashes helped with growth and some blooms.

Pests

Does wood ash have any pest repelling properties? I’d love to find a natural remedy for killing/repelling ants, DE doesn’t seem to work. All the ants have decided to move their nests into all my outdoor (and some indoor!) potted plants. They don’t seem to be harming the plants, but their numbers are getting out of control. Any advice would be appreciated!

Ants

Ants can be beneficial but if you are having a problem with them use a Boric Acid powder along their trails. They will take it back to the colony and you'll soon see them disappear. It is relatively cheap and not harmful to humans and pets. I picked up several bottles at the dollar store to have on hand when needed.

wood ash

very good thank you

Ants are as good as earthworms

Ants perform many of the same soil improving functions as worms do, and can be even more effective and prolific due to their numbers. Their tunnels and chambers aerate and help drain the soil, they break down organic matter into ideally sized particles filled with beneficial microbes from their gut, and they can help moderate soil pests. If they are not fire ants, or getting in your food, or ranching aphids, I'd be thankful for them. Carpenter and other ants also get a bad wrap regarding structure damage, as they only occupy already rotten, wet structurally weakened wood, causing little additional harm, and their trails back and forth to their chambers are giving you an indication of a problem that you may have otherwise not known about until it collapsed from rot.

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