If you burn brush in the spring or wood in your fireplace in the winter, then you may have some ashes lying around. A resourceful gardener would think about recycling these ashes somehow.
So, can you put wood ashes in your garden? Yes, you can put wood ashes in your garden. Wood ashes will help to fertilize soil by providing phosphorus, potassium, and calcium, among other nutrients. Wood ashes can also be used in place of lime, to raise soil pH. However, you need to be careful about the source of your wood ashes, since some commonly used wood is chemically treated.
Wood ash has numerous benefits and uses in your garden, but there are also some cautions to observe when using it. Let’s start with the benefits and uses of wood ash.
Can You Put Wood Ashes In Your Garden?
Yes, you can put wood ashes in your garden, since they can be a great addition to your soil. After all, plants and trees grow back after a wildfire, which “cleans the slate” and allows new growth.
Wood ashes can provide nutrients, and can also be used as an alternative to lime to raise soil pH.
There are some cautions to observe when using lime (more on these later).
If you decide to add wood ash to your garden, plan to apply it in winter or early spring. For more information on using wood ash in your garden, check out this article on wood ash from the University of Vermont Extension.
What Are The Benefits and Uses Of Wood Ash In Your Garden?
As mentioned earlier, wood ash can be used as fertilizer and can be used in place of lime. It can also be used in a compost pile or on your lawn.
Wood Ash Is A Good Source of Nutrients (Fertilizer)
Wood ash contains some of the nutrients that plants need to grow, including phosphorus and potassium (the P and K in NPK). Wood ash also contains plenty of calcium, which is another important nutrient for plants.
The NPK content of wood ash is about 0-1-3 (0% nitrogen, 1% phosphorus, and 3% potassium by weight). This means that wood ash does not contain any nitrogen at all (the nitrogen is released as gas when wood is burned).
This means that you can use wood ash as a fertilizer when you don’t want to supplement nitrogen. If you have ever had plants grow tall and green without flowering or fruiting, you know that too much nitrogen can be a problem. For more information, check out my article on low-nitrogen fertilizers.
On the other hand, if you do want to add nitrogen to your garden, you can supplement wood ash with grass clippings and then compost the mix to create a nice, nutrient-rich mixture for your garden.
Wood Ash Can Be Used To Raise Soil pH (Use Wood Ash Instead Of Lime)
Normally, gardeners receive the advice to add lime (calcium carbonate) or dolomitic lime (calcium magnesium carbonate) to soil in order to raise the pH. However, wood ash also has the effect of raising pH. Remember though that wood ash is less effective than lime at raising pH.
In fact, you would need twice as much wood ash as lime to raise your soil pH. For more information, check out my article on raising soil pH.
For further reference: the Old Farmer’s Almanac suggests using one 5-gallon bucket of wood ashes per 1000 square feet of garden.
Oregon State suggests that one cord of wood will produce enough wood ash for a 30 foot by 30 foot square garden (an area of 900 square feet).
You Can Put Wood Ash Into Your Compost Pile
Instead of adding wood ash to your soil, you can put it into your compost pile. There, it will break down and combine with the other material in your pile, giving you a more uniform mixture to apply in your garden.
Just make sure not to add too much at once, or else you could spike the pH too high. This could hurt worms and bacteria that help the compost pile to decompose. Instead, add the wood ashes gradually over time.
For more information about what you might not want to compost, check out my article on composting eggshells and other common kitchen waste.
You Can Use Wood Ash On Your Lawn
Most people need to lime their lawns on occasion to raise the pH. If you have enough wood ash, you can use that instead.
At the very least, you can supplement lime with wood ash to reduce the amount of lime you need to buy at the store. Just make sure to apply ash to your lawn on a day without wind – check the weather forecast ahead of time!
Cautions About Using Wood Ash In Your Garden
Although wood ash has many helpful uses in your garden, there are also some cautions to observe before you go about spreading it around.
Wear A Mask and Goggles To Handle Wood Ash
Always protect your eyes and lungs when working with wood ash or any other dusty substance. Otherwise, it can cause eye or lung irritation.
As an added layer of precaution, don’t shovel, move, or apply wood ash in windy weather. When you apply wood ash, rake it into soil lightly, or turn it slowly into your compost or soil with a shovel to avoid stirring up clouds of ash.
Also keep in mind that wood ash is very water soluble. Make sure to store the wood ash in a container, and keep it sealed until use. Otherwise, rain can leach away the nutrients in the wood ash pile.
Avoid Certain Types of Wood Ash
If you burn natural wood that you cut yourself, then there is no need to worry. However, certain types of wood ash may be contaminated, depending on the source.
Any wood that is painted, finished, or pressure treated will contain chemicals that you don’t want to breathe in while burning. The wood ash may still contain these chemicals after burning, so you don’t want to use it in your garden.
You should also avoid ashes from plywood, pallet wood, and wood pellets, since these are often treated with chemicals as well.
You definitely do not want to use ashes from a fire where you burned trash, such as plastic or other potentially harmful materials. If you aren’t sure, forget about using the ashes in your garden and start fresh with your next brush fire or campfire.
Wood Ash Can Raise pH or Add Salts To Soil If Concentrated
If you have clumps of ash or add too much in an area, you can raise the pH too high. Most plants have an ideal pH range, outside of which they will have trouble absorbing certain nutrients from the soil.
If you aren’t sure about the soil pH, make sure to do a soil test before adding anything (wood ash or otherwise) to your garden. For more information, check out my article on doing a soil test.
Wood ash may also add salts to the soil, which can be harmful to plants in high concentrations. This is especially true for seedlings and younger plants that are more susceptible to burning by excessive nutrients or fertilizer.
To avoid this, don’t put wood ash directly into the soil near seedlings. Instead, add wood ash to your compost pile, and then turn the mixture into the soil before the planting season begins.
Wood Ash Nutrient Content Varies By Type Of Wood
It goes without saying that each type of wood will have a different nutrient content and chemical composition. In turn, the ash from burning this wood will vary in its nutrient content.
The wood ash may also vary in its pH depending on the source of the wood used for the fire. To avoid a pH imbalance, add a little less wood ash than you think you need to lime the soil. Then, wait a while and observe the effect on the soil pH.
If you still need the pH to be higher, you can add a little more wood ash. This is one benefit of preparing your garden early, so that you have time to adjust pH and nutrients as needed without rushing the job.
Don’t Use Wood Ash Near Acid-Loving Plants
Since wood ash can raise pH considerably, you don’t want to use it near plants that prefer acidic soil. Most plants prefer slightly acidic soil, with a pH in the range of 6.0 to 6.8 (slightly acidic to neutral).
However, blueberries and azaleas prefer a pH closer to the range of 4.5 to 5.5. Similarly, potatoes prefer a range pH range of 4.8 to 5.5. Avoid using wood ash near these plants, since you can accidentally raise the soil pH too much in a short time, leading to a very short season for these plants.
By now, you have a pretty good idea of the benefits of using wood ash in your garden. You also know what to avoid, and how to make sure the wood ashes you use are safe for your soil.
I hope you found this article helpful – if so, please share it with someone who can use the information. If you have any questions or advice of your own about wood ashes in the garden, please leave a comment below.