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COLUMN: Garden success and soil pH

Mary Anne Lorenz, Master Gardener Volunteer
Posted 3/19/23

One of the biggest factors affecting the health of plants in your garden is the pH of the soil, which is a measure of acidity.

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COLUMN: Garden success and soil pH


One of the biggest factors affecting the health of plants in your garden is the pH of the soil, which is a measure of acidity. If the blueberries or azaleas in your garden always seem sort of sad, soil pH is probably affecting them. Understanding, measuring and adjusting pH are important for the successful garden.

The pH scale runs from 0 (most acidic) to 14 (most alkaline), with 7 as a neutral pH. Anything below 7 is acidic; anything above is alkaline. The pH scale is logarithmic: a pH of 6 is 10 times more acidic than a pH of 7, and 100 times more acidic than a pH of 8. Soil pH determines how easily your plants can take up nutrients from the soil around them. If soil is too acidic, necessary phosphorus becomes less available, and aluminum levels may increase to toxic levels. If soil is too alkaline, essential nutrients like iron, copper and zinc become less available, leading to poor growth and yellow leaves.

Most garden plants prefer a slightly acidic soil with pH between 6.0 and 7.0. Certain plants like azaleas, rhododendrons, and blueberries absolutely require acidic soil (around pH 5.5) and will not thrive in anything else.

So, what is the pH of your garden soil? A soil pH test should be taken every two or three years. To do this, take a sample of soil at various locations in your garden in a random pattern. Dig each hole six to seven inches deep and remove a ribbon of soil from one side of the hole. All soil ribbons should be mixed thoroughly in a clean pail. Bring about one cup of the combined soil in a plastic bag to Cornell Cooperative Extension Oneida County where it can be tested for a fee of $2 (if you are located out of the area check with your local Extension office). Your soil test report will indicate whether adjustments need to be made in your garden.

If your soil is too acidic, lime can be added to raise the soil pH and should be worked into the upper 4-6 inches of soil. Many gardeners prefer to add lime in the fall, to allow the slow adjustment of pH to occur before spring planting. If you need to lower the pH for acid-loving plants like blueberries and rhododendrons, elemental sulfur can be worked into the soil in the spring. Lowering the soil pH is a slow process that may take years. The recommended amounts of lime or sulfur will be found on your soil test report and the chemicals can be purchased at garden stores.

Creating a beautiful, bountiful garden requires planning, patience, and creativity with a touch of chemistry mixed in. Measuring and knowing your soil pH is an important step of the process.

Cornell Cooperative Extension Oneida County answers home and garden questions which can be emailed to or call 315-736-3394, press 1 and ext. 333. Leave your question, name and phone number. Questions are answered weekdays, 8 a.m. to 4 p.m. Also, visit our website at or phone 315-736-3394, press 1 and then ext. 100.


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