I first learned about using wood ashes in my garden from a friend from Kenya. We were walking in the garden and noticed that the kale was infested with aphids (which often happens in the heat of the summer around here). I’m always leery of using chemicals so i usually end up doing nothing. I asked her what they used in the garden in her village and she said, “Wood ash.”
And that was when I began using wood ashes in the garden.
What is Wood Ash and Where to Get It
Wood ash is exactly what it sounds like it is…ashes from burned wood. It’s full of nutrients that can be used as fertilizer in the vegetable garden, on fruit trees, and even the lawn.
While you can purchase wood ash at your local garden center, a better place to get it is from any wood burning source in your home such as…
- fireplace ashes
- wood burning stove
- outdoor fire pit
- smoker
- brush burn
Unless you’re trying to raise the ph of very acidic soil, you really don’t need a lot of wood ash for the garden. So, don’t overlook small wood burners like the smoker. Over time those small amounts will add up.
If you want wood ash that has the most nutrients, the type of wood burned matters. Hardwood has more nutrients than wood from softwood, therefore, ashes of hardwoods will have more nutrients than ashes of softwoods. But all wood ash has is a good source of potassium and other trace elements.
Benefits Using Wood Ashes in the Garden
- Rich in Minerals: Wood ash is a rich source of trace elements such as calcium carbonate, potassium, magnesium. These nutrients are vital for plant growth, flowering, and fruiting.
- Very Alkaline: Wood ash has alkaline properties, making it an excellent amendment for acidic soils. If your vegetable garden’s soil is too acidic, adding wood ash can help balance the pH of the soil. Just know that it will take about twice as much wood ash as it does agricultural lime to change the soil pH. So, if you test your garden soil and it recommends 20 pounds of lime be added, you’ll need 40-50 pounds of wood ash.
- Natural Pest Repellent: Wood ash can act as a natural deterrent for certain pests. Sprinkling a thin layer around plants can help keep pests at bay without resorting to chemical pesticides.
The main nutrient in wood ash is potassium, the third number listed on a fertilizer analysis. It’s left behind in the form of “potash” (potassium bicarbonate). Adding wood ash to a garden plot also adds calcium and magnesium to the soil, similar to applying lime.
University of Georgia
How to Use Wood Ash in the Garden
While wood ash is really great to use in the home garden, it can cause trouble if over used or used on plants that like acidity.
Test and Amend the Soil
It’s recommended that before applying wood ash, you do a soil test to check the soil’s pH. This will help you determine whether your garden needs a pH adjustment and how much wood ash is required. If you’re trying to amend the soil, then you definitely need a soil test. You can send a soil sample off to a lab or do an at-home soil test. However, if you’re using wood ash in small quantities for things like pest control, a soil test is not necessary (in my opinion.)
Like most other soil amendments, it’s best to use wood ash in the late winter or early spring before planting. As a soil amendment, wood ash works more quickly than lime and only needs about a month to work. So, if you’ve missed the window for using agricultural lime as an amendment, you can use wood ash.
When spreading wood ash on the soil, try to spread it on moist soil so it stays where you put it. If the soil is dry, gently water it after spreading the ash.
As a general rule, don’t use wood ash as an amendment for soil that has a pH of 6.5 or higher as it will make the soil too alkaline for most fruits and vegetables. That being said, if you’re growing something that needs more alkaline soil, using wood ash is a good thing.
Wood ash can also be used along with other organic matter to help break up clay soil.
Sprinkle, Don’t Dump
Sprinkling the wood ash on the soil or plants ensures that you won’t get it concentrated in one area and kill the plants in that area. If you’re treating a large area be sure to use a rake to evenly spread the wood ashes over the soil.
Application Rates
Wood ash fertilizer should be used according to the rates below to raise the ph level of the soil.
- For gardens and flower beds apply 15 to 20 pounds of wood ash per 1000 square feet. This about the amount of finished ash you can get from burning one cord of wood.
- For rose bushes and fruit bushes apply 1/2 to 1 pound of wood ash around the base of the plant.
- For individual plants apply wood ash around the base of the plant to no more than 1/2-inch thick
- For fruit trees apply wood ash around the base of the plant to no more than 1-inch thick
Add to the Compost Pile
Wood ash can be added directly to the compost heap. It will help control the acidity of the compost and you’re more likely to end up with a compost that is near neutral on the pH scale. It not only enriches the compost with valuable minerals but also ensures a more gradual release of nutrients into the soil.
Wood ashes can also help with odors that sometimes happen in a compost pile as it’s breaking down organic matter. And it helps with the texture and tilth of the finished compost.
Wood Ash for Pest and Disease Control
One of my favorite uses for wood ash in the garden is pest control — it’s free, it’s always on hand, and it works without chemicals. Wood ash works as a pest deterrent in two ways: it’s abrasive, which damages the soft bodies of insects, and it’s highly alkaline and desiccating, which dries them out on contact. It also loses effectiveness when wet, so reapply after rain.
Slugs and snails — sprinkle a ring of dry wood ash around the base of plants. Slugs won’t cross it. This is especially useful for lettuce, kale, and other leafy greens that slugs love. Reapply after rain.
Aphids — dust wood ash directly onto aphid-infested leaves. The abrasive particles damage their soft bodies and the alkalinity deters them from settling back in. I keep wood ash in an old parmesan cheese container so I can sprinkle it precisely. Try to avoid getting ash into open blooms where bees are foraging.
Ants — sprinkle wood ash around the base of affected plants or along ant trails. It won’t kill a large colony on its own but it disrupts their paths and deters them from setting up around your plants. Works best as part of a broader approach for heavy infestations.
Squash bugs and flea beetles — dust ash on the leaves and around the base of squash, cucumbers, and other vulnerable plants early in the season before infestations take hold. An old-fashioned trick is to mix wood ash with a small amount of salt — my grandmother’s generation used this on beans to deter beetles.
Powdery mildew — because wood ash is alkaline it can help control fungal diseases including powdery mildew. At the first sign of powdery mildew on your squash or cucumbers, dust the affected leaves with ash. It won’t cure an established case but it can slow the spread significantly, and I’ve had good results catching it early.
Blossom end rot on tomatoes — if your tomatoes are showing blossom end rot, mix a small amount of wood ash into the soil around the base of the plant. The calcium in the ash helps address the deficiency that causes blossom end rot.
One important note: when applying ash to plants, be careful around open blooms. Bees and other beneficial insects visit flowers and you don’t want to coat them in ash. Apply to leaves and soil, not flowers.
Plants That Like Wood Ash (and Plants That Don’t)
Because wood ash raises soil pH and adds potassium and calcium, it’s a great fit for plants that prefer neutral to slightly alkaline conditions — and something to keep well away from plants that need acidic soil.
Plants that benefit from wood ash
These plants appreciate the minerals and slightly elevated pH that wood ash provides:
Asparagus is one of the best candidates — it thrives in alkaline soil and responds well to the potassium and calcium in wood ash. Apply it around your asparagus bed each spring.
Brassicas — cabbage, broccoli, cauliflower, Brussels sprouts, and kale all do well with wood ash. It also helps deter some of the pests that commonly attack this family of plants.
Tomatoes benefit from the calcium (which helps prevent blossom end rot) and potassium (which supports fruiting). A light application around the base of the plant is plenty.
Garlic and onions both appreciate the potassium boost that wood ash provides and grow well in the slightly alkaline conditions it creates.
Roses and lilacs are classic wood ash plants — gardeners have been feeding them with ash for generations. Apply around the drip line in early spring.
Spring flowering bulbs — tulips, daffodils, and crocus all respond well to wood ash, even in soil that’s already neutral.
Most fruit trees benefit from wood ash applied around the drip line. Apply no more than an inch thick and keep it away from the trunk.
Plants that don’t like wood ash
Keep wood ash well away from these:
Blueberries, cranberries, and other acid-loving fruits need a soil pH of 4.5–5.5 to thrive. Wood ash will raise pH and can seriously stress or kill these plants. If you grow blueberries, keep all ash well away from their root zone.
Potatoes — wood ash can encourage potato scab, a fungal disease that causes rough, corky patches on the skin. Skip the ash entirely for potatoes.
Sweet potatoes prefer slightly acidic soil and don’t benefit from the pH increase that wood ash brings.
Azaleas, rhododendrons, and camellias are acid lovers that will struggle in the more alkaline conditions wood ash creates.
Seedlings of any kind — the high salt content in wood ash can burn tender seedlings. Wait until plants are established before applying. If you’ve made compost with wood ash mixed in, that’s fine to use around seedlings since the nutrients are more diluted and buffered.
Safely Using Wood Ash
Wood ash should be completely cooled before using or storing. Once it’s cooled you can sift out any unburned wood chunks and then either use the ash or store it for later.
When using wood ash (or any fine powder) you should wear a dust mask to keep from inhaling the particles. Its a good ideas to wear gloves, especially if you plan on touching the ash with your hands. We always think about acidic things burning but alkaline things can also leave burn.
Also, if you’re unsure about what was actually burned, don’t use the ashes. You want ashes from just untreated wood – no charcoal or briquettes, no plastic or styrofoam, no fake wood from the fire place, no treated or painted wood.
Heavy Metals in Wood Ash
Properly sourced wood ash rarely has heavy metals in it. Metals such as cadmium and lead can sometimes be present in wood ash, however, the rise in pH in the soil from using wood ash will often keep the plants from taking up the heavy metals. That being said, if you’re concerned about the wood ash you’re using you can have it tested.
Source: University of Wisconsin-Madison
Storing Wood Ash
If you’re not going to use wood ash right away, you can store it in a metal container. If you have lots of ash, for instance from wood-burning stoves, you can use a galvanized trash can. If you don’t have much, you can use a galvanized bucket with a lid, which is what we do. Just make sure the ash is cool before you put it in the bucket.
The main thing is that the wood ash needs to stay dry. If you leave it out in the open, the nutrients can leach out when it rains.
More Practical Uses for Wood Ash
As mentioned before wood ashes are very alkaline and if you remember anything from your high school chemistry class, hopefully you remember that alkaline substances (also called base) can cause chemical burns, just like acidic substances. The further substances are away from neutral (ph 7) the harsher they are. There is certainly not reason to be scared to use wood as in a variety of ways, but you do need to be prudent.
Because it’s alkaline, it makes a very good household cleaner. Mix with a little water to scrub pots and pans, sinks, bathtubs, toilets, glass and silverware. Anywhere you’d use something like Bar Keeper’s Friend.
Lye is extracted from wood ashes and is essential for soap making.
It can be be sprinkled on oil spills to help with clean up.
Wood ash can be sued as a roach repellant. I wouldn’t use it in my home but we do use it in the hen house.
Add wood ash to your chicken’s dust bath area to help control mites, fleas and other insects.
Wood ash can also be to preserve food – seeds, tomatoes, and even cheese.
In a pinch, it can be used for wound care and to help relive the itch from insect bites.
Frequently Asked Questions
Yes — wood ash works as a natural pest deterrent in a few ways. It’s abrasive, which damages the soft bodies of insects like slugs and aphids. It’s also highly alkaline and desiccating, meaning it dries out insects that come into contact with it. Sprinkling a ring of dry wood ash around the base of plants creates a barrier that slugs and soft-bodied insects won’t want to cross. For aphids, dusting ash directly onto affected leaves can deter and kill them. Just avoid applying it to open blooms where beneficial insects are feeding.
Wood ash can deter ants when sprinkled around the base of plants or along ant trails. It’s not a guaranteed ant killer, but the alkaline, abrasive nature of the ash is uncomfortable for ants and can disrupt their paths. Reapply after rain since moisture neutralizes the effect. For heavy ant infestations, wood ash works best as part of a broader approach rather than as a standalone solution.
Plants that thrive in alkaline or neutral soil benefit most from wood ash. Good candidates include asparagus, brassicas (cabbage, broccoli, cauliflower, Brussels sprouts), tomatoes, roses, lilacs, garlic, and most fruit trees. These plants appreciate the potassium, calcium, and slightly raised pH that wood ash provides. Spring-flowering bulbs like tulips and daffodils also respond well to wood ash.
Avoid using wood ash on acid-loving plants — it will raise the soil pH and stress them. Plants to keep wood ash away from include blueberries, cranberries, azaleas, rhododendrons, camellias, potatoes (it can encourage potato scab), and sweet potatoes. Also don’t apply wood ash directly to seedlings, as the high salt content can burn them.
Yes — tomatoes benefit from wood ash in a couple of ways. The potassium supports fruiting and the calcium helps prevent blossom end rot, which is a common problem caused by calcium deficiency. Mix a small amount of wood ash into the soil around the base of your tomato plants, or add it to your compost to release it more gradually. Don’t overdo it — a thin sprinkling is plenty.
Yes, as long as you burned only untreated natural wood. Fireplace ash and fire pit ash are both fine. What you want to avoid is ash from treated or painted wood, charcoal briquettes, fake logs, plastic, or styrofoam — these can introduce harmful chemicals into your soil. If you’re not sure what was burned, don’t use it.
Less than you’d think. For general soil amendment, apply 15–20 pounds per 1,000 square feet — about what you’d get from burning one cord of wood. For individual plants, a thin layer no more than ½ inch deep around the base is plenty. It’s always better to apply a little and reapply than to dump a lot at once. Too much wood ash raises soil pH too high and can lock out nutrients that plants need.
Wood ash raises soil pH — it makes soil more alkaline. This is helpful if your soil is too acidic (below 6.0), but can be harmful if your soil is already neutral or alkaline. Before using wood ash as a soil amendment, it’s worth doing a simple soil pH test. If your soil pH is already 6.5 or higher, skip the wood ash as a soil amendment and save it for pest control or compost instead.
Yes — wood ash is a good addition to compost in moderate amounts. It helps neutralize acidity, adds potassium and calcium, can reduce odors, and improves the texture of finished compost. The key word is moderate — don’t dump large amounts in at once as it can make the pile too alkaline. Sprinkle it in as you add other materials rather than adding it all at once.
Angi Schneider is the author of The Ultimate Guide to Preserving Vegetables and Pressure Canning for Beginners and Beyond, both published by Page Street Publishing. She has taught canning classes for 177 Milk Street, been featured in Serious Eats, and written for Countryside Magazine. Angi has been sharing gardening, preserving, and simple living skills since 2010.
You can make lye with hardwood ash for soap making. I wonder if the ash will keep grasshoppers away.
I have been using wood ash for a couple of years now and had great success. I add it into the soil before planting too.
Ash also has the benefit of insulating the ground whatever you cover at the ground level.
interesting article. Our soil is naturally alkaline but I still sprinkle a handful in my compost pile whenever I start over by adding lots of leaves, etc., etc.
I usually just burn a few old tires I have laying around and sprinkle what’s left afterwards around the perimeter of my house. I have had no problem the past 5 years!
In Texas it’s illegal to burn tires, but even if it weren’t I wouldn’t recommend it. The ash that is left isn’t good for your ground water or soil and the black smoke isn’t good for the air. If, for some reason, you can’t recycle the tires, I would suggest making swings for your children and neighborhood children (http://creativesimpleliving.com/make-a-tire-swing-for-some-frugal-family-fun/) and only using wood ash in the garden.
He was joking. Lighten up.
I certainly hope he was joking! However, tone of voice isn’t communicated very well in writing, so unless you say you’re joking we have no idea. So, because I choose to publish and respond to every comment, even ones I don’t agree with I choose to reply with another option. I’m certainly not mad and don’t need to “lighten up”, but I don’t want people reading this article and think it’s okay to burn your tires.
Peat is bogging down the conversation. ?
This thread was funny. I needed that.
Glad it made you laugh!
Oh Gosh I hope Derek was just joking!!
Me, too!
Thanks for the information I will be starting a garden next year
You’re welcome. I hope your garden goes great!
Thanks so much for the great advice! I am assuming wood charcoal from a Big Green Egg is acceptable. My first real vegetable garden this year, have done herbs and tomatoes in pots before, so doing lots of research!
How exciting! As long as you are certain it’s just wood. We don’t use charcoal so I’m not sure if anything else but wood would be in there.
I take the ash from my fireplace and always throw it in the garden rather then throw it away. My garden is real healthy and I have very little problem with pests. I plant marigolds and other plants to deter pests. For instance I plant dill (which attracts aphid eating ladybugs) close to plants susceptible to aphids.
Those are great ideas, Brian. I love that you’re using a multi pronged approach to deter pest. Thanks so much for sharing!
Even in an alkaline soil wood ash is great for spring flowering bulbs ..tulips,daffodils, crocus..
Thanks for sharing, Elaine. I’m not much of a flower gardener and didn’t know that.
What is the difference between wood ash and sulphate of potash in its composition and effects on vegetables?
The main differences are going to be cost and precision. If you use ashes from wood you burned, it’s free but you won’t know the exact percentage of potash or potassium in it. If that doesn’t bother you to not have that precision, I would just use wood ash. On the other hand sulphate of potash costs money but the bag will tell you what percentage of potash and potassium are in it. If you need that specificity or don’t have access to wood ash, then use sulphate of potash. The effects of using either one are going to be very similar.
Yes I use ash on my plants. It’s a very old technique followed by se people here in india. It’s too popular. Many people are using ash left from burning cow dung cakes.
I have collected ash from burning dried leaves of neem tree. This time I have used it on my plants at terrace and results are too good
I can suggest one more item for farming which is self made and costless. We call it jeevamrut. It’s a good fertilizer.
Hi Sharad, it’s really great that your people are really utilizing what’s available for fertilizer. Here in the states I think most of us (myself included) don’t realize how wonderful those fertilizers are and instead spend money on purchased fertilizer and pesticides. I looked up jeevamrut and it looks amazing – I’ll have to see if I can locate some local cow dung to try some. Thanks so much for sharing what you do!
My grandmother used wood ashes sprinkled thru an old hose (think panty hose). On beans to get rid of beetles. The mixture was a peck of wood ashes filtered thru a wire strainer to a half cup of salt (or I quart to a tablespoon for my much smaller garden). It works and I just set up my recipe today to be ready.
Thanks for the tip!