Soil Quality and pH

• Garden soil is either acid or alkaline and pH is the measurement of each. Acidic soils have a pH of 3.5, being very acidic, to 6.5, being slightly acidic. Alkaline soils range from 7.4 to 9.0. Neutral is between a pH reading of 6.6 and 7.3. Soil pH affects the available plant nutrients and a pH between 6 and 7 fits the most common plant need. Some plants do prefer a high acid soil, while others favor a soil higher on the alkaline side. Adding wood ash to the soil alters the pH and affects plants in different ways.
  
  

Plants That Do Not Like Wood Ash

• Because wood ash raises alkalinity, it reduces acidity, which for some plants is fine, but for acid-loving plants the use of wood ash can severely damage or kill the plant. Do not add wood ash where blueberries, rhododendrons, azaleas, or potatoes are grown. These all need high acidity to thrive. Blue hydrangeas also need higher acid soil to remain blue. Any plant that requires a high-acid environment suffers from the addition of wood ash to the soil.
  
  

Adding Wood Ash to the Garden

• Wood ash contains many nutrients essential to plant growth, and adding wood ash to the garden is beneficial to all but acid-loving plants. Burning hardwoods will produce more ash than softwoods, and hardwoods have a higher nutrient content. Add up to 1 lb. of wood ash to each shrub or rose bush in the spring, and spread the ash evenly around perennials, raking or digging it into the top level of the soil. Test the soil pH level before adding wood ash to ensure the garden is getting the nutrients it needs. Do not apply to lawns if the pH is higher than 7 as the grass may burn. For lawns with a pH of less than 7, apply up to 15 lbs. of wood ash per 1,000 square feet.
  
  

Wood Ash and Pest Control

• The addition of wood ash to the compost pile promotes a neutral pH, the ideal condition for the microorganisms that live within the compost to break down the organic material provided, and also provides additional nutrients to the compost. Wood ash also can be used as snail and slug pest control as the ash pulls the water from the insects body. Lightly sprinkle around the base of plants to help reduce snail and slug damage to plants.