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One of the greatest results of a soil test is the valuable information it provides of what plants will grow and won't grow on your site. Keep in mind the zone hardiness must be considered first but pH of the soil and its available nutrients is a critical factor if a species of plants will work or not.
How pH works
or soil reaction is an indication of the acidity or alkalinity of soil and is measured in pH units. Soil pH is defined as the negative logarithm of the hydrogen ion concentration. The pH scale goes from 0 to 14 with pH 7 as the neutral point. As the amount of hydrogen ions in the soil increases the soil pH decreases thus becoming more acidic. From pH 7 to 0 the soil is increasingly more acidic and from pH 7 to 14 the soil is increasingly more alkaline or basic.
Soil pH Affects Nutrients, Minerals and Growth
The effect of soil pH is great on the solubility of minerals or nutrients. Fourteen of the seventeen essential plant nutrients are obtained from the soil. Before a nutrient can be used by plants it must be dissolved in the soil solution. Most minerals and nutrients are more soluble or available in acid soils than in neutral or slightly alkaline soils.
As the pH reaches that high scale many available nutrients are simply tied up chemical and they will not be available for plant growth. Soil pH is a measure of soil acidity or alkalinity. The balance between hydroxyl and hydrogen ions determines pH. Soil pH is important because it affects the availability of plant nutrients, toxic elements, and soil microbes. Many woody plants will actually be able to survive in soils with a wide range of pH, from about 4.5 – 8.2.
But for optimal health and growth, most trees and shrubs do best with a soil pH of 6.0 – 7.0. (The exception is acid-loving plants which prefer a lower pH of 4.5 – 6.0.) The trees listed to the right prefer a pH of 6.0 – 7.0, but will still perform admirably under alkaline soil conditions up to a pH of about 8.2. It is important to identify alkaline-tolerant trees because many urban soils are high in pH.