Soil pH – Lowering
Q: I want to plant azaleas and rhododendrons in a spot where I had a vegetable garden last year. We had the soil tested last year and found the pH to be 6.1. Since azaleas love acid soil, what should I do to lower the pH?
A: Maybe it would help to describe azaleas as acid -tolerating rather than acid-loving. These plants and their kin have grown in shady, wet woodland conditions for thousands of years. Over time, their roots evolved the ability to absorb nutrients in soil that is more acid than most plants find favorable. Azaleas grow well in soils that range in pH from 5.0 to 6.0. Most plants, though, like a pH of 5.5 to 6.5.
Since your pH is more than 6.0, you’ll need to acidify your soil. Wayne Mixon, in the Scotts Fertilizer research department, says Miracid alone will not acidify soil. It only slightly accelerates the downward trend in acidity that most Georgia soils undergo. He recommends excavating a hole three feet wide and one foot deep for each plant and mixing a 2 gallon bucketful of sphagnum peat with the soil. Also mix in eight tablespoonfuls of wettable sulfur (available at garden centers). Return the mixture to the hole and plant your shrubs normally, watering them thoroughly afterwards. In this way the soil pH will be lowered and your azaleas and rhododendrons will thrive.