When Can I Put Lime on My Yard?

What Is pH?

• Soil is either acidic or alkaline, and pH is a measure of that. The pH scale goes from 0 to 14, with 7 being neutral. Low numbers are acidic, while high numbers are alkaline. Acidic soil limits the availability of nutrients to plants. Alkaline soil has the opposite problem; there is not enough acid in the soil. If your lawn is alkaline, do not try to improve it using lime.

What Is Lime?

• In the context of gardens and lawns, lime refers to agricultural lime, which can take the form of either calcitic lime or dolomitic lime. While calcitic lime is composed mainly of calcium carbonate, dolomitic lime also has magnesium in it -- typically at least 6 percent. It is usually obtained by grinding natural limestone. This substance usually comes powdered for easy application with a rotary spreader or drop spreader, devices that ensure an even dusting of lime over the surface of your lawn or garden.

Application Times

• You can apply lime at almost any time of year. It is most effective if you apply it while preparing soil for planting. Because lime moves slowly through soil -- it can take up to two years for lime to penetrate 2 inches -- this is your best opportunity to ensure a thorough, even distribution. If you need to apply lime after grass is growing or a plant is installed, that's OK. The best times of year are fall, winter and spring, in that order. It isn't harmful to apply in summer, it just won't be effective when the soil is completely dried out. Do not apply when the ground is saturated, though, as lime may clump.

On the Lawn

• Although lawns vary in their pH preferences depending on turf grass species, most lawn grasses prefer a slightly acidic or slightly alkaline growing environment. If your pH range is between 5.8 and 7.5, most lawn grasses will survive. Outside those ranges, lawn grasses may not be able to access the nutrients they need, and can grow sickly and disease-prone. Avoid this by testing your soil. Gather soil samples from 10 or so places around the lawn, mix them together and use a home testing kit to determine pH.

In the Garden

• Lime is less commonly used for garden plants than for lawns, but if your soil is too acidic then you may need lime for edibles and ornamentals as well as grass. Most ornamentals are fine with acidic soils, but many vegetables grow well at pH levels between 6.0 and 7.0, so if your pH is lower than that, you may need to add lime. Lime amounts vary depending on the original pH level and soil type, but generally speaking, more lime is needed as soils move from sand to loam to clay. For a sandy garden that has never been limed, for instance, apply 4 pounds per 100 square feet.