Acid-loving Plants

Posted by Katie Elzer-Peters
June 5th, 2009
Filed in Soil and Fertilizer
Tags: acidity, fertilizer, Soil and Fertilizer

Acid-loving plants are not plants on drugs; they are plants growing in acidic soil.  Whether a soil is

considered “acidic” or “basic” is entirely dependent on the pH of the soil.  (Don’t get the pH of the soil confused with adding “humic acid” to your soil, though humic acid is derived by lowering the pH of a solution with humus in it to separate solids from liquids.  For more on humic acid and the way it affects plant growth, see the post about humic acid.  Have I lost you?)

The pH of the soil makes a big difference in the health and growth of certain plant varieties.  Some plants are happy in a fairly broad pH spectrum, while others grow much better on the acid side of the pH scale.  Plants that like acid soils are happiest in soil with a pH of between 4.5-6.0.  While technically, any pH below 7 is considered acidic in chemical terms, true acid-loving plants are happier at a much lower pH.  In North America, soils in eastern and Pacific Northwest/ British Columbia areas are acidic.  Soils in the arid west and southwest are alkaline.  Just because your soil is alkaline doesn’t mean that you can’t grow acid loving plants, but you do have to do some soil amendment work.  Soil pH affects nutrient uptake in plants-each nutrient is most available at a specific pH level, as shown by the above diagram.  If your soil is naturally on the acidic side, then you are in luck, and can grow the following plants:

Soil pH North America Red=Acid, Blue=Alkaline

Plants that Thrive in Acid Soil

Acid soil is, technically, called acidic soil.  Here are some plants that are happiest in acidic soils.

Trees and Shrubs

• Azaleas
• Rhododendrons
• Blueberries
• Clethra
• Fothergilla
• Holly
• Dogwood
• Beech
• Pin Oak
• Willow Oak
• Gardenia
• Raspberry
• Grape

Annuals, Perennials and Vegetables

• Strawberries
• Japanese Iris
• Trillium
• Begonia
• Caladium
• Radish
• Sweet potato

Hydrangeas: the pH Oddball

Have you noticed that one shrub border full of the same hydrangea plants can display flowers ranging from pink to purple to true blue?  That is a phenomenon caused by pH differences of the soil in one location or another.   The blue color in hydrangeas is caused by uptake of aluminum, which is most available at a soil pH in the acidic range (below 5.5).  In soils with a pH higher than 5.5, the flowers will turn pink.  Now, there are a lot of different hydrangea cultivars, some of which have white flowers.  Those flowers won’t turn pink or blue.

Changing the Soil pH

It is easier to manipulate the pH of soil in containers, because the container characteristics depend entirely on what you, the gardener, put into the container.  In general, if you want to raise the pH of your soil (make the soil more alkaline), you will add lime.  If you want to lower the pH of your soil (make the soil more acidic), add sulfur.  You can purchase garden-friendly lime and sulfur at your local garden center or farmer’s supply store.