What Are Ashes Good for In a Garden?

  • Ashes make good fertilizer.
  • Ashes can deter pests, like slugs and snails.
  • Ashes can help keep weeds down.
  • Ashes are good for the garden soil.
  • Ashes can be used to control plant diseases.
  • Ashes are good for flower beds.
  • Ashes help repel insects and other bugs away from your garden.
  • Ashes can be used as mulch around plants in your garden or yard.
  • Ash makes excellent compost!

Ashes are alkaline, so they’re good for breaking up clay soils and neutralizing acids in soil.

If you are a gardener, there are many useful things to know about ashes in the garden. Gardeners with clay soil will be happy to know that ashes improve soil drainage, while those with acidic soil will appreciate the fact that they can use it to neutralize their soil. This is because wood ash is alkaline, with a pH between 6 and 8. Ashes are high in potassium, which is essential for good growth of plants, flowers and fruits of all types; one pound of wood ash contains 10 percent potassium oxide–and therefore 10 percent potassium by weight. The high amount of potassium found in ashes makes them quite valuable as a fertilizer; however, there are some caveats.

Wood ashes can safely be used with other organic materials (manure, compost, leafmold, etc.) to improve soil structure and aeration.

You can test your soil’s pH by picking up a testing kit at a hardware store, or you can take a soil sample to your local extension office. Another plus of using wood ash is that it has some nutrients that plants need and use such as potassium, calcium and magnesium.

Wood ash is high in potassium, but since it also depends on what type of wood was burned for the ash, the amount of potassium can vary considerably. They’re also slightly alkaline, which will raise the pH level in soil if you have acidic soil. If you have an alkaline soil wood ashes are not recommended because they will make it more alkaline.

Wood ashes are good for plants such as blueberries and apples that prefer slightly acidic soils; blueberries and apples tend to grow poorly if the soil pH is too high (which means it’s too alkaline). However, gardeners in areas with naturally high-pH soils should avoid adding wood ashes to their gardens. The ash would further raise their soils’ pH levels beyond an acceptable range for most plant species.

Wood ashes add potassium to the soil which helps with overall plant health and growth.

A wood ash garden application is an easy way to add potassium to your soil. Potassium helps plants use water, which in turn produces lush growth and disease resistance. It’s also a key player in plant photosynthesis, which is the process of plants converting water and carbon dioxide into food.

Potassium can benefit all kinds of plants, including trees, shrubs, vegetables, fruits and ornamental plants. If you mix wood ashes with water or compost before adding them to the soil, they will release nutrients more slowly than if you simply spread them on top of the ground as a mulch.

The high potassium content of wood ash also stimulates flowering.

If you’re wondering what ashes to add to the garden, then you either have a fireplace or a wood stove. If you’re new at this, then don’t worry: Ashes are easy to work with and have many benefits.

Plants that can benefit from wood ash include tomatoes, peppers, rhododendrons, strawberries and other plants that like their soil alkaline. Soil tests will help determine if adding ash is right for your garden—or if it would be better to leave well enough alone.

Wood ash contains calcium carbonate (aka lime) so it helps raise the pH of acidic soils. One cubic foot of ashes contains about 20 pounds of lime—roughly equivalent to one-third of a pound per plant.

Use wood ash as a pre-emergent weed killer.

You may have used wood ash as a pesticide or compost activator, but did you know you can use it to prevent weed growth? Wood ashes help soil pH veer away from the acidic side and toward neutral pH level. Your soil will already be at a neutral pH if it’s been treated with lime, so don’t add wood ash if that’s the case.

Not all weeds require alkaline conditions to thrive, but some do. Here are some common garden weeds that do best when your soil is on the alkaline side:

  • Dandelion
  • Chickweed
  • Clover

You can use wood ash as a pre-emergent weed killer by spreading it on top of moist soil in areas where weeds are likely to grow and keeping an eye out for new growth. To apply, sprinkle the ashes evenly over the soil and rake them in gently without tilling them too deep into the ground. Be careful not to use too much or you could kill desired plants nearby instead of just weeds!