The Best pH Levels for Growing in the Earth

General Levels

• Most plants, including vegetables, ornamental plants and grasses, prefer soils with a pH between 5.8 and 6.5, according to Clemson University Cooperative Extension. This pH range is considered slightly acidic. At these ideal pH levels, most nutrients are widely available and easily assimilated by plants. Although these levels are ideal, most plants will grow in soils with a pH between 5.8 and 7 without requiring any soil amendments.

Special Plant Requirements

• Some plants require extreme pH conditions. Blueberries, gardenias, rhododendrons and azaleas, for example, are commonly referred to as acid-loving plants, since they prefer soil pH conditions lower than 5.5, which is considered to be very acidic. Many trees, including juniper, cypress, dogwood, pine and laurel trees, also prefer acidic soil conditions, although they do not require them. Other plants, such as boxelder, hackberry, barberry and locusts will tolerate alkaline soil conditions, according to Bachman's website.

Testing Your Soil

• For optimum plant health and development, get your soil pH tested before planting. Home soil pH tests can be obtained from your local home and garden center. However, taking soil samples to your local university extension provides a much more thorough soil analysis that includes pH testing, nutrient level tests and recommendations about how you can improve your garden soil. If you have very acidic or alkaline soil conditions, a laboratory analysis may also provide recommendations about plants that will tolerate these conditions.

Amending Your Soil

• If your pH levels are moderately high or low, there are steps to take to amend your soil. To increase soil pH, most gardeners apply liming materials. Liming materials include ground limestone, hydrated lime and pulverized lime. Wood ashes may also increase soil pH. To decrease soil pH, apply aluminum sulfate or sulfur. Don't over-apply soil amendments, since this can cause plant damage. As noted by the University of Florida IFAS Extension, sometimes the best way to deal with very acidic or alkaline conditions is to stick with plants suited to these environments.