Plants are like people in regards to their taste preferences – some like sour foods and some like sweet foods. And that’s where the pH level of soil and its affect on plant growth comes into play.
Soil with a high pH level is sweet soil, low pH is sour soil, and all plants have their preference.
Knowing the soil pH and what each plant prefers, then matching the right soil and plants, will help ensure optimum growth and health.
pH Scale
Soil pH is measured on a scale that ranges from 1-14, and most plants grow best in the 5.5 -7.5 range.
The higher the number on the scale the more alkaline is in the soil, and the lower the number the more acidic the soil. pH 7 is neutral.
Alkaline Soil
Alkaline soil (sweet soil) contains a lot of sodium, magnesium and calcium, but is limited in other nutrients.
Alkaline soil is not very soluble, making it difficult for plants to uptake the few nutrients that are in the soil. Plants grown in alkaline soil are often stunted and produce poorly.
What Makes Alkaline Soil?
Areas where water contains a lot of lime will cause soil to become alkaline.
Dense forests and arid desserts also have high alkaline levels in the soil.
Amending Alkaline Soil
The acidic level can be raised by incorporating sulfur and/or organic matter into the soil. This will lower the pH level and make the soil more fertile.
Plants for Alkaline Soil
Some plants thrive in alkaline soil. Clematis, honeysuckle, geranium, daisy, hyacinth, lilies, iris, Boston ivy, morning glory and poppies are a few that prefer sweet soil.
Acidic Soil
Acidic soil (sour soil) occurs when too much calcium and other nutrients have been leached of the soil by an abundance of rainfall or by over-watering plants.
Over-fertilizing also increasing acid in the soil. The soil will have a sour odor when worked.
Wooded areas where there is a lot of organic matter decomposing is naturally high acidity.
Amending Acidic Soil
Acidic soil can be sweetened by incorporating garden lime in the soil. This is a white powder substance that is easy to work into soil.
Plants for Acidic Soil
Hydrangeas, Colorado blue spruce, azaleas, rhododendrons, mountain laurel, nasturtium, bleeding heart, and tomatoes grow best in soil that is slightly high on the pH scale.
pH Test
pH testing is done with a simple soil test kit and will alert you to the type of soil you have. You can get one from your local nursery.
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