Characteristics of Acidic Soils

Soil acidity determines the health of the flora you introduce into your landscape. As a general rule of thumb, if a soil pH test reveals a value below 7.0, you have acidic soil. Values above 7.0 usually denote alkaline soil, whereas a result of exactly 7.0 indicates neutral soil conditions. It is tempting to visit the home improvement store or nursery in search of soil amendments that will neutralize the pH level of your soil even if it is close to 7.0; before you do so, a quick look at the characteristics of acidic soils may convince you to not change a thing.

Risk of Toxicity

Plants require a favorable soil pH to take up nutrients, build strong root systems and thrive. Soil pH levels that are slightly acidic result in a better nutrient availability to plants, since nutrients and minerals dissolve more easily in this soil; however, if your soil’s acidity is too high, this advantage actually turns into a drawback. Your soil then experiences oversaturation with some otherwise beneficial minerals and nutrients. This overdose of iron, aluminum and also manganese may be toxic to many of your plants. For example, high levels of soluble aluminum exist in soil when the pH level reaches—or drops lower than--5.5. An overdose of soluble aluminum leads to plant root deterioration in some species, which in turn prevents the plants from absorbing the nutrients and water they need to properly grow and thus stunts their growth.

Growth Support

Moderate soil acidity favorably impacts the growth and health of some plants, but even higher acidity can still sustain plant life. Prior to introducing new plants into your landscape, check the soil pH and then shop for flora that will do well in your soil. For example, bog rosemary prefers acidity levels of 4.0 to 5.0 and wheat thrives in soil with a pH of 5.0. Bleeding heart grows well in areas with levels ranging from 5.0 to 6.5. Heather and heath need a pH between 5.0 and 6.2; grasses prefer a level of 5.5, and legumes thrive in soil with a pH of about 6.5. Astibles, foxglove and bergenias do well in soil with a pH range from 5.5 to about 6.5. If your soil pH drops below 4.0, you will need to consider adding amendments to make it hospitable to even the more acid-loving plants.

Changeable With Lime

If you do determine that your soil is so acidic that it cannot adequately sustain plant life, add lime as a soil amendment to raise the pH level. The easiest way to introduce this substance into your soil is by purchasing commercially available lime pellets and spreading them onto the soil with the help of a manual spreader. Work the lime into the top 6 inches of soil with a rake or rototiller, water it in and give it some time to dissolve. Base the quantity of lime on the makeup of your soil and its current pH level. For example, to raise the 5.0 pH level of clay soil to a future pH of about 6.5, you need to spread 15 pounds of ground limestone for every 100 square feet of soil.