Understanding Soil pH

pH is a measure of the relative acidity or alkalinity. Soil pH is a big deal when gardening, as the relative pH affects the availability of ALL the plant nutrients. Good soil for vegetable and flower gardening has a pH between 6.5-7 (relatively neutral). Here is how the pH spectrum breaks down:


Most gardens require regular additions of lime to “sweeten” or raise the pH of the soil. This is because the plants’ extraction of nutrients, and the build up of organic matter overtime just naturally tends toward acidity. See Ask Ruth from June 2009 to read about liming your garden, and the different types of lime available.litmus test

You can learn the pH of your soil when you do a regular soil test through NCDA, or, you can test the pH yourself with a home kit. The litmus kits tend to work better than the digital readers, but both are available through local garden center retailers like Reems Creek Nursery

If you’re facing alkalinity problems, you’ll need to add sulfur to the soil, but be very careful doing this, and seek assistance from a knowledgeable party, as too much sulfur can be toxic to your garden.

Also note that certain plants have a pH preference. Blueberries, for example, love acidic soil, so plant accordingly, and know that plans for companion planting may be challenged by acidic conditions, unless you choose the species wisely. Hydrangeas can change their color based on the pH of the soil, and you can use this knowledge to adjust to your preference. Sweet soil produces pinker blooms, and acidic soil produces blue flowers. And it doesn’t stop with hydrangeas. As you become more advanced in gardening, you can play with soil pH in the garden and in containers to cultivate and feature particular plant species.

Most gardeners in Appalchia will find that the pH of their soil ranges from 4.5 (acidic) to 8 (quite alkaline). Because the range is so great, be sure to test your soil annually, and apply lime as needed, usually in the fall.