How to Use Wood Ashes in the Garden

how much wood ash in raised bed?If you have spare ashes lying around from a backyard fire pit, recycle some of it into your soil! Two hundred years ago, ash was processed for use as a potash fertilizer source. Eventually, the production became more costly and new methods to produce potash were developed.

Why might ashes be good for the garden?

Depending on source, wood and plant ashes contain varying amounts of potassium, phosphorus, magnesium and micronutrients. Calcium is the most abundant element in wood ash so it acts somewhat like agricultural lime. In fact, it is stronger than lime. The best way to use wood ash is as a long term soil amendment – never a short-term feeding solution. Ash helps keep water in the soil which in turn helps nutrients work more efficiently with each other. Also add ash to the compost pile.

What kinds of ash works best?

Ashes from hardwoods (oak) and softwoods (pine) can be used in the garden. Hardwoods will contain more nutrients than the same amount of softwood ashes.

What kinds of ash should I avoid?

Do not use ashes from treated, stained or pressed wood products. Particle board contains glues and formaldehyde. I would also not use wood ashes from wood that had any kind of fire starter poured on it.

Charred plant matter can be used in the garden as well. I tend to forget things in the oven so I’m a veteran of burned plant matter – otherwise known as dinner!

Which plants may benefit from wood and plant ashes?

Cabbage, broccoli, kale, kohlrabi and collards may benefit from soil amended with ash. Young plants or newly emerged seedlings could be damaged by ash. It’s best added to the soil well before planting.

Combine wood and plant ashes with compost. Use small amounts of ash and large amounts of compost. I can’t stress enough that if you use too much ash in your garden, you risk killing your plants and damaging your soil. So, please use it in moderation and when in doubt use less than more.

How do I prepare ash for the garden?

I place the ash in a plastic bag and crush with a brick or rock. Smaller pieces will make it less concentrated and easier to disperse.

Are there any warnings when working with ash?

Use gloves and a dust mask unless you can be super careful not to touch it with your bare hands or breathe in dust particles. Don’t work with ash on dry, windy days. Fresh ash could still be “live”. Only use ash that is cool and completely burned-out to prevent skin burns and a fire hazard.

How much ash should I use?

For a raised bed measuring 8 feet x 4 feet limit the wood ash to 3 – 4 cups. As you can see, you don’t need much. Don’t add more than a tablespoon per gallon of soil. If you’ll be adding it to a large compost heap, for example two cubic yards of compost, then plan to work only 6 – 8 cups of ash into the pile at one time.

When is the best time to apply ash?

The best time to apply ash is before you plant, at least a couple of months out. This could mean late fall or early spring. Disperse it evenly and rake it in under the surface. Avoid leaving ash on the surface. It is more effective when it contacts the soil.