by Effie Moore Salem

Created on: July 29, 2010

Effective gardening, or even successfully growing flowers on the front porch, demands that growers have a basic knowledge of the makeup of the soil. Soil pH  (potential hydrogen) means that all soils are of three different types, acidic, neutral, or alkaline. This is measured from 0-14 with 7 being the neutral, or balanced soil. Generally most gardens grow best in the 6-7 range. The lower scale from 0 to 7 is acidic, the higher scale, 7-14 is alkaline.

Acidic soils

Acidic soils are soils that are made up with acid causing minerals. In areas where heavy rainfall leeches out calcium and other alkaline materials, acid soils prevail.  To counteract this, farmers spread fine ground limestone over their fields in the autumn and by the next growing season,  the soil pH will nearer a near level of 6 to 7. This is simply a routine chore with farmers.

Small gardening plots or individual pots where the plants are not thriving can be treated with additions of compost or some other alkaline source. As a minuscule example, to increase the alkalinity of a hanging basket of petunias where excessive rain has leeched out the nutrients, boil eggshells and water with this a few times, and watch the plant begin thriving. Egg shells are alkaline and these should never be thrown away but added to the compost heap, or buried in pots of growing plants where over acidity is suspected.

Some few plants need an excess of acidity in order to thrive. Hydrangea plants with blue flowers are sure to have a soil somewhere on the lower end of the scale at around 4.5. Without this added acid, the flowers will resort to pink. Pink hydrangea blooms need only the pH of around 6. Azalea, camellia, and gardenia plants require heavy acid soils. An available source of acid for these plants is the coffee grounds that is most often discarded each day.

Neutral soil

Neutral soil is neither too acid or too alkaline. It is balanced. Each of these two is in equal amounts. Most soils are either slightly one of the other and that still is considered neutral enough for most vegetables and plants. The soil pH is never static and is changing according to the weather conditions and the activity of the microorganisms in the soil.

 Heavy rains, often in themselves acidic  because of the heavy pollutants in the air, and because of the leeching effect of nutrients due to run off, will cause neutral soils to become too acidic, therefore requiring additions of calcium. Pepper plants, as an example, may suffer from being too acidic and will fail to thrive.

Alkaline soils

Alkaline soils are found in areas where limestone is prevalent in rocks, as opposed to sandstone, as an example. These soils tend to have more clay in them and clay soils drain poorly, if at all. To make them more porous, add sand. This is important. Soils that are not porous enough for proper drainage will not permit interaction of microorganisms, and nutrients needed for growth will be lacking.

A few plants such as asparagus and ferns desire  alkalinity, but they are the exception. Most plants grow better if the soil is slightly acid, somewhere around five or six. Those who understand the makeup of the soil can look at the type of plants growing and figure out quite accurately the condition of the soil. Most gardeners, however, must keep a chart handy, pasted on the refrigerator, or close by, of the pH of each plant.

Learn more about this author, Effie Moore Salem.
Click here to send this author comments or questions.