Down & dirty facts on soil pH

Down & dirty facts on soil pH

Soil acidity, or pH, affects how well plants can use nutrients in the soil. A pH reading of 7.0 is neutral.

Readings above 7.0 (such as 7.6) indicate the soil is alkaline. Readings below neutral (such as 5.2) indicate the soil is acid.

You can make soils more alkaline by adding 3 to 5 pounds of ground agricultural limestone to each 100 square feet. You can make soils more acid by adding 1 to 3 pounds of finely ground sulfur to each 100 square feet.

Landscape plants’ preferences

These are 15 commonly used landscape shrubs, trees and flowers and their preferred pH ranges:

Azalea, 4.5 to 6.0

Begonia, 5.5 to 7.5

Crape myrtle, 5.0 to 6.0

Day lily, 6.0 to 8.0

Dogwood tree, 5.0 to 7.0

Geranium, 6.0 to 8.0

Hydrangea (blue), 4.5 to 5.0

Hydrangea (pink), 6.0 to 7.0

Iris, 6.5 to 7.0

Magnolia tree, 5.0 to 6.0

Pine tree, 5.0 to 6.0

Redbud tree, 5.5 to 6.5

Red oak tree, 5.0 to 7.5

Tea roses, 5.5 to 7.0

Zinnia, 5.5 to 7.5

For a more complete listing of soil pH preferences for 78 common landscape plants, along with a fertilization table, pick up a free copy of the handout “Soil pH and Fertilizers,” available from county agents with the Mississippi Cooperative Extension Service.

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