pH of Alkaline Soil

Detecting Alkaline Soil

• The simplest way to determine whether soil is alkaline is to take a sample of the soil and have it tested. Soil tests are available in garden supply centers or may be submitted to county extension offices. Plants that grow in alkaline soil sometimes give visible clues as to the culture in which they're grown. For example, signs of iron and zinc deficiencies often cause yellow stripes on middle or upper leaves. Signs of phosphorus deficiencies may result in purple or dark green coloring of the leaves, according to Colorado State University Extension.

Problems with Alkaline Soil

• An imbalance of pH, too high or too low, reduces the availability of certain nutrients. For alkaline soils, it is a reduction of zinc, iron and phosphorus, according to Colorado State University Extension.

Amending Alkaline Soil

• For highly alkaline soils that measure above 8.0, it may be necessary to amend the soil to lower the pH. To do so, add organic matter such as sphagnum peat moss or peat. Once a year, add elemental sulfur, 6 to 10 lbs. for every 1,000 square feet. Plant in sandy beds on a raised medium or use acidifying fertilizers, recommends Utah State University Extension.

Plants for Alkaline Soil

• Some perennials that thrive in alkaline soil include plants in the genus Helleborus, such as the Helleborus x hybridus "Lenten Rose," and the genus Sciabiosa, such as the Sciabiosa Columbaria "Pincushion flower," according to Horticulture magazine. Deciduous shrubs that fare well in alkaline soil include Syringa vulgaris "lilacs," and shrubs that belong to the Forsythia genus. Buxus Hybrid "Green Velvet boxwood" and Ceanothus spp. "California lilacs" are good evergreen shrubs for alkaline soil.