Do Snapdragons Prefer Acidic Soil?

About Acidic Soil

• The acidity or alkalinity of soil is rated on a 0.0-14.0 scale of pH values. Testing pH measures the potential hydrogen ions present in the soil water. The lower the pH value number, the more acidic the soil. The higher the pH numbers indicate alkaline soil. Any pH measurements close to a 7.0 value are considered to neutral. Knowing your soil pH is important because some plants grow better in acidic soils, while others prefer alkaline or neutral soils to thrive. Soil testing kits are available at local garden centers or through the area's extension service.

Low pH and Snapdragons

• Snapdragons thrive in soil with a slight acidity level of pH 6.0 to 6.5, but can tolerate pH levels as low as 5.5. When growing snapdragons, the soil should be rich and loamy to drain well. The more acidic soil also helps the nutrients within the soil, such as nitrogen, phosphorus and potassium, be more water-soluble and easier for the roots to take up. However, these vital nutrients become more water-insoluble at pH levels less than 5.5 with the plant roots unable to extract the nutrients.

High pH and Snapdragons

• When the soil pH level is higher than 7.2, it is alkaline. The higher the alkaline level, nutrients like phosphorus, iron and manganese become water-insoluble. The effect of a high-alkaline soil on snapdragon plants is poor root development, stunted and malformed growth, and poor flower development.

Remedies

• Test your soil to determine the existing pH value before adding any amendments. Soil tests are available at local garden centers or local cooperative extension services. Adjust the garden soil's pH before planting snapdragons by adding appropriate supplements. Ground limestone added to acidic soil, 1 lb. for one square yard, raises the pH value. To lower the pH value of alkaline soil and add acid, work compost into the garden soil. Pine needles are particularly useful for this purpose because the needles are very acidic. Sulfur can also be used to lower the pH, but it takes about a year. Spread a layer of sulfur or limestone and then use a shovel to work the supplement into the soil to a depth of 10 to 12 inches.