Butterfly bushes (Buddleja spp.) offer growers a fragrant, colorful addition to the yard that attracts butterflies. These flowering shrubs are vigorous growers, reaching the mature size of 6 to 10 feet tall and 4 to 10 feet wide in one to two growing seasons. They make excellent additions to butterfly gardens in U.S. Department of Agriculture plant hardiness zones 5 through 9. Butterfly bushes thrive in areas with full sun with well-drained soil and the proper pH level.
Before planting the butterfly bush, you can conduct a soil test to determine the pH level of the soil. These bushes require a pH level between 6.0 to 7.0, which is in the slightly acidic range, and one preferred by most plants. Based on a soil test, you can use lime to amend the soil and raise the pH or use sulfur to lower the pH level. Soil that is highly acidic with a pH level of 4.0 or lower is generally inhospitable to most plants.
Why pH Level Is Important
Like other plants, the pH level can determine what nutrients are available for plants. Providing butterfly bushes with the proper pH level ensures the shrubs receive necessary nutrients from the soil, grow well and increase the plants' resistance to pests and disease. Soil pH also determines whether the soil contains beneficial insects, such as earthworms that help the permeability, aeration and porosity of soil. Beneficial organisms cannot live in highly acidic soils.
pH and Nutrient Deficiencies
Soils with a high pH level which causes alkaline soil can cause deficiencies in certain nutrients, such as iron and manganese. Soils with a low pH or acidic soil can cause deficiencies in copper, boron and zinc. Symptoms of nutrient deficiencies in butterfly bushes vary, but can include yellowing of leaves, wavy, curly or crinkled leaf margins and undersized leaves. If you notice signs of nutrient deficiency, conduct a soil test to determine if the pH level is higher or lower than recommended for butterfly bushes.
What Affects Soil pH levels
The amount of rainfall an area receives, the type of soil and mulch used all play a role in the soil pH level. Areas with soil near driveways, roads or concrete structures often contain more lime and have a higher pH, or alkaline, soil, while sandy soils that receive heavy rains experience leaching and often have a lower pH, or acidic, soil. Some types of organic mulch can affect pH levels, such as pine needles, which can make soil more acidic as they decompose.
- The New Illustrated Encyclopedia of Gardening Volume 4; T.H. Everett, Ed.
- Clemson Cooperative Extension: Butterfly Bush
- The New Sunset Western Garden Book; Kathleen Norris Brenzel, Ed.
- University of Florida Hendry County Horticulture News: pH Problems Produce Peaked Plants
- University of Wisconsin Cooperative Extension: Manganese Deficiency - Woody Plants
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