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.
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