During the winter months, we heat our house entirely with wood. It’s a popular heating choice up here where the trees are plentiful and the winters are long and bitterly cold. But even if you’re winters are practically non-existent, wood ash can build up in your fire pit or out door fireplace. Fortunately, there are great options for using wood ash in and around the garden, so nothing goes to waste.
After a few bonfires, or after 7 months of snow storms, what do you do with all that wood ash? If your ashes are starting to pile up around the fire pit, it might be time to start sharing the wealth. Your garden will love soaking up a bit of potash from all those fires.
What is Wood Ash Good For?
Gardeners have been mixing a bit of wood ash into their soil since the agricultural revolution. In fact, ashes from wood fires are ideal for increasing the potassium levels in your garden, and balancing acidic soil.
Without adequate potassium levels, your plants are more vulnerable to diseases and pests. Potassium helps your plants absorb and transport water effectively. As a result, plants without a balanced potassium intake often produce smaller, tougher produce. Without the right levels of potassium, that juicy cucumber you’ve been looking forward to tasting will be fibrous and bitter.
Some plants have higher potassium needs than others. Have you ever tried the trick of burying banana peels around your roses? It really works! This is because roses crave potassium. They often suffer from a lot of diseases and pests as well, and nothing helps boost your plant’s immune system like potash.
Balancing Soil PH
I live in the the piney wood hills of New England, and my soil is acidic. Our tall pines love acidic soil, but most of our garden does not. With wood ashes, we can balance the pH without having to buy a commercial additive.
In fact, wood ash is starting to replace lime as a way of neutralizing acidic soil. It works almost as well as lime at balancing pH levels, and wood ash adds trace minerals that aren’t in the lime. Furthermore, some reports claim that wood ash can boost growth up to 45 percent more than limestone.
Nutrients of All Shapes and Sizes
We already know that wood ash is full of potassium, but it has other macro and micro nutrients as well. Ashes will generally register somewhere around 0-1-3 on a traditional fertilizer label. That means they’re providing no nitrogen, some phosphorus, and more potassium.
If you use a lot of composted manure as fertilizer, wood ash is a great balancer. Manure is often heavy in nitrogen, moderate in phosphorus, and low in potassium. Ashes also bring magnesium into the mix, which is essential for helping plants build chlorophyll.
Using Wood Ashes in Your Garden
We know that they’re beneficial, so now let’s figure out how to use ashes in the garden! There are a few different methods for using wood ash in your garden. The method you choose will depend on how soon you need to boost potassium and balance pH. It’s also determined by how many little piles of ashes you have to work with.
My favorite way—because it’s so easy—is to just add the ashes to the compost bin. Remember, we pile up ashes all winter long, so I can’t exactly add them to my snow-covered garden directly. Instead, I’ll dump an occasional bucket of ashes on top of the compost pile.
The ashes neutralizes any odors and aid in decomposition. They boost the compost’s fertility and help it to break down faster. It’s important to add wood ashes to your compost slowly—a sprinkle better layers is better than a whole ash bucket at a time. Too much wood ash at a time can make your compost bin too alkaline, killing off the worms and helpful bacteria.
When I’m worried about overdoing it, I sprinkle the ashes in the outhouse, or on top of slick, icy snow. Wood ashes can give great traction on ice. But, if you burn wood with nails in it, make sure to sift those out before driving over the ashes.
To lime your garden with wood ash, just add the ashes to your soil directly. You usually don’t need to add much, but test your soil first to know where it falls on the pH scale. If your soil is very acidic, you’ll need more ashes; less acidic, you’ll need fewer.
If your soil is neutral or alkaline, do not add wood ash. It’d be so sad to disrupt the balance of your soil by adding anything unnecessary. If you need to boost potassium levels in soil that’s already alkaline, try fertilizing with bananas or coffee grounds instead.
3. Pest Control
Wood ashes’ pH balancing and potassium boosting benefits aren’t the only way to use them your garden. While they’re the primary uses of wood ash, there are other benefits. For example, ashes are deadly to slugs and snails. They can also deter other soft-bodied invertebrate pests.
Sprinkle wood ashes around the base of your plants. They salts in the ashes actually dissolve slugs and snails, and dehydrate many other salt-sensitive invaders. These destructive pests can’t pass the ash barrier to get to your delicious cabbages and squashes.
When to Avoid Adding Wood Ashes to the Garden
No fertilizer is universally applicable. Wood ashes can be incredibly helpful, when they’re needed, but you should make sure that they’re the right addition to your garden. If you’re growing acid-loving plants, for instance, you’ll want to find a non-alkalizing additive.
In addition, not all plants prefer balanced soil. While most garden plants prefer neutral soil, some plants—like blueberries and azaleas—are happiest in acidic soil. Adding wood ash will make their soil inhospitable to them.
If your soil is already alkaline, wood ash will throw it even more out of balance. Try adding sphagnum peat moss or sulfur to the soil to bring it closer to neutral instead. When soil is too extreme in either direction, it becomes toxic to most plants. We definitely don’t want toxic soil, so always check your garden’s pH levels before supplementing with anything.
Ashes By Any Other Name?
Wood ashes are the only ashes that are safe to use this way in the garden. If you’ve been burning charcoal or pellets or other burnable products, the ashes aren’t going to be safe for your garden.
If you light your fires with junk mail, or occasionally burn up old bills or love letters, that’s not a problem. Everyone adds paper to their fires. Those ashes are just as safe and healthy for your garden as all wood ashes. It’s only when you start burning pressure-treated wood, charcoal, or other chemically altered burnables that your ashes become suspect.
Painted wood is also something to use in moderation. If you’re burning a lot of old barn boards and painted siding, be careful. This is because older paint is often lead-based. Burning lead painted boards will both release lead dust into the air and contaminate your ashes.
It’s always better to dispose of wood painted with lead properly. Acrylic paint is definitely safer, but it’s also essentially plastic. Avoid burning too many acrylic painted boards in your fire if you’re hoping to reclaim the ashes.
Particle board and finger jointed wood has a lot of glue holding it together. Like painted wood, burn particle board sparingly if you’re planning to use ashes in the garden. The best fires for producing garden ashes are made from split firewood, not leftover building material.
Hard & Soft
Hardwoods like oak, ash, maple, and birch usually burn longer and cleaner than soft woods like pine, fir, and spruce. Hardwoods also produce ashes with a higher potassium and pH levels than softwoods. Probably because of the tighter grain in the wood. If you’re hoping to neutralize highly acidic soil, hardwood ashes are going to produce better results.
Gathering Fertilizer in the Cold Seasons
As summer shifts into fall, we start to light our stove in the evenings and put the garden beds to rest. As each bed is harvested and mulched for winter, I have a fresh bucket of wood ashes to mingle with manure and leaves.
This late-season liming application of ashes helps balance my soil for next year’s garden. The ashes, along with manure and leaves, are scratched into the soil by marauding chickens, then covered by the first snowfall. As we burn through our wood pile each winter, I like to sprinkle ashes in the compost bin to keep our compost healthy and balanced.
We live in a snow-heavy climate, so I can rarely turn he compost through the winter. In spring, when I can turn my compost at last, I have rich, black soil—perfect for filling pots and feeding indoor plants.
It’s a wonderful, natural system that allows the winter’s excess of ashes to feed the summertime gardens. Ashes are a great way to balance your soil sustainably. You’re reclaiming some of nature’s bounty to build a self-sufficient garden!