Blueberries and azaleas are woody perennials that require sun to partial shade and moist but well-drained acidic soil. Because blueberries and azaleas are both acid-loving shrubs, this message explains their soil pH needs and offers amendment ideas.

What is Soil pH?
Soil pH is a measurement that tells us a soil's acidity. A pH below 7 indicates an acid soil, while a value above 7 indicates soil that is alkaline. A pH of exactly 7 is called 'neutral'. Blueberries and azaleas perform best with a pH of 4.5 to 5.5. Soils with a pH higher than 5.8 may cause iron chlorosis. You'll notice yellowing near leaf veins. If your initial soil pH is 7.3 or higher, you may find it difficult to create a suitable environment for acid-loving plants, even with amendments.

Soil pH should be adjusted BEFORE planting, so conduct a soil test to determine your soil's initial pH.

If the pH is too high…

• Prior to planting, mix four to six inches of acid sphagnum peat into the upper six to eight inches of soil. Positive effects last six to ten years.
• Elemental sulfur lowers pH and may be added at the rate indicated by a soil test. Because elemental sulfur reacts slowly, it should be worked 8 to 10 inches into the soil the year before planting.
• Iron sulfate also lowers pH. It reacts faster than sulfur but is more expensive, mostly because you apply it at seven times the rate of elemental sulfur.
• Although aluminum sulfate is available in garden centers and also lowers pH, it can be toxic to roots. There are better choices.

How much sulfur should be applied?

The amount of sulfur or iron sulfate you will apply depends on the initial soil pH and whether your soil is sandy or loamy. Use your soil test results to determine the appropriate rate.

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