Because we heat our home with wood, we have an abundance of wood ashes. In fact, we generally scoop a 5-gallon bucket of ashes out of our wood-burning stove every few days. After dumping the ashes for awhile, we started wondering if there could be a better way to use them. We compost all sorts of other things – kitchen scraps, grass clippings, and what have you… What about composting ashes?? If you’ve also been wondering if ashes are good for compost, keep reading and we’ll tell you what we’ve learned about the practical uses of this nutrient-packed material.
Are Ashes Good for Compost?
Ash is full of nutrients, such as potassium and calcium, that make it a great addition to your garden compost. However, the type of ash you use is very important. While fireplace ashes can provide valuable nutrients to your soil, you should never compost ashes from charcoal or treated wood.
Ashes from treated or painted wood, charcoal ashes, or coal ashes can contain harmful chemicals and heavy metals that can be dangerous for your soil and potentially toxic. Of course, these materials are not something we want to be putting into our soil that helps to produce the food we’re going to eat.
Because of this, you should always use untreated wood when composting for your garden soil.
What Will Ash Do to Your Soil?
Composting ashes allows you to add nutrients to your soil that will make it healthier and in turn boost your soil health – for many plants. Because ashes are quite alkaline, adding them to your soil will lower your soil’s acidity level. Many times, this can be really helpful, because the pH values of compost are often low, meaning that compost is often very acidic. Adding ashes can lower the acid soil and help balance out your soil’s pH.
As a quick science lesson, remember that acidic soil has a pH of 7 or less, and alkaline soil has a pH of greater than 7. It’s a great idea to test the pH of your soil if you’re wondering whether or not you should add ashes to your compost. A simple pH meter from Amazon is an easy way to do this, or you can even do a DIY soil test and check the your soil pH with materials you probably already have lying around the house.
What plants like composted ashes?
Although a number of plants may appreciate the ash compost, not every type of plant thrives with lower acidity levels. Some acid-loving plants, like blueberries, azaleas, sweet corn, cucumbers, and certain herbs may struggle with high acidity. Plants that do enjoy composted ashes include lavender, lilacs, rosemary, and thyme, as well as many others that you probably have in your vegetable garden, like tomatoes, asparagus, broccoli, cabbage, and brussels sprouts. So, be mindful of where you’re spreading your ash compost.
In addition, keep in mind that just because some plants prefer lower acidity doesn’t mean that you should drown them in composted ashes. Too much ash can over-fertilize your plants and actually harm the soil. Add ash in moderation, and do a soil test if you’re not sure.
The Type of Ashes You Use Matters
Please keep in mind that the types of ashes you use matters greatly! While wood ash and even paper ash can be an excellent addition to your compost material and a great source of extra nutrients for your garden plants, the addition of ash from other materials can really harm your soil.
For the home gardener, it’s important to keep ashes from treated wood, painted wood, charcoal, and coal away from your garden beds. Because of the harmful chemicals contained in these materials, it can be dangerous to eat produce grown near soil that contains these chemicals.
How to Compost Your Ashes
So, what’s the best way to compost your ashes? Should you add them to your compost pile? Or spread them directly on the soil?
If you have the ability to do so, mixing your ashes in with your other compost is the easiest way to assure a good balance. Remember that, as you compost, you want a good ratio of brown material (such as ashes, wood chips, straw, etc.) to green material (food scraps, manure, grass clippings, etc.). Brown materials are richer in carbon, while green materials are more nitrogen-heavy. Everyone has a different opinion on this ratio of brown to green, but as a general rule, something like 1:1 works for most situations.
Don’t get too stressed about it. Just don’t load down your compost pile with a large amount of wood ash without mixing other organic materials (both brown and green) into your compost heap. Too much ash will cause your compost heap to become too alkaline. Spreading a small amount of ash between every foot or two of compost will likely be enough.
(So unfortunately for those of you with a wood stove, like us, the large amounts of leftover ash from your wood burner may be way more than you need, unless you have a lot of compost. Sadly, too much of a good thing is no longer a good thing! Thankfully, there are other ways you can use your ash compost, too. Keep reading to find out how!)
As a good rule of thumb, unless your soil has very low pH, you shouldn’t apply ash directly to your plants. However, if you’ve tested the pH level of your soil and found it to be below 6.5, go ahead and apply some ash directly.
If you’re using ashes from a wood stove, it’s very important to keep in mind that the ashes need to be completely cooled before spreading them in your compost pile. Depending on how you store your ashes, they can stay hot for a few days or even more. And of course, smoldering ash in your compost pile could be very dangerous!
FAQ About Composting Ashes
What are some other uses for wood ashes?
If you have too much ash for your compost bin, don’t worry! There are lots of benefits of wood ash besides using them for soil amendment. Here are a few other ways to put your ash to good use.
- Bug repellant. If you’re having pest problems, spread your ashes around the affected area. It’s great for repelling bugs such as slugs, snails, and even ants.
- Soap making. For hundreds of years, people have used ash to make lye for soap.
- Stain remover. Ashes are great for soaking up unwanted moisture. You can apply ash on oil stains on hard surfaces such as concrete or asphalt to help remove the oil.
- Traction. If your vehicle is stuck in the snow, spreading a few cups of wood ash can be a great way to provide traction for your tires.
How can I make wood ash tea?
Compost tea made ashes is another great use of wood ash that can be beneficial to your plants. You can easily make this by filling a cloth or burlap back with 30 pounds of wood ash and then “brewing” it in 30 gallons of water. A garbage can works well for this.
When your tea is ready, pour a cup around the plants that will most benefit from this alkaline mixture. Compost tea can be easier and sometimes less messy than regular compost when it comes to spreading wood ash compost on particular plants.
What’s the best way to store wood ashes?
An ideal way to store wood ashes is in a metal container. After removing ash from a fire, be sure to set your ash bucket on cement or brick rather than a wood deck or porch. In fact, it’s a good idea to keep your ash a few feet away from any combustable surfaces. Remember that parts of the ash can stay very hot for up to a few days or even more.
Can I compost wood ashes from a fire pit?
Sure. Composting wood ashes from a bonfire/outdoor wood fire has just the same affect as using ashes from an indoor wood stove. Just make sure that you’re using pure wood ash and that there was no treated wood or other toxic ashes mixed in to your bonfire ash.
What other materials are good for compost?
Looking to improve your compost pile and therefore improve your soil health? It seems like there’s no end to the amount of materials that you can compost. Here’s a short list of everyday items you might use in your kitchen or around your property that can be a beneficial addition to your composting process.
Green materials:
- Coffee grounds
- Grass clippings
- Fruit and vegetable scraps (for best results, use uncooked fruit and vegetable scraps)
- Fresh manure (just be sure to compost this first rather than applying it directly to your garden
- Extra plant growth
Brown materials:
- Leaves
- Hay
- Straw
- Sawdust
- Shredded paper
- Cardboard
- Eggshells
- Tea bags
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