Can You Apply Lime Anytime to a Flower Garden?

Understanding pH

• The pH is a measure of the acidity or alkalinity of a material. A pH of 7.0 is neutral, while a pH of 8.0, for example, is alkaline. Peat moss, from highly acidic bogs, has a pH of around 4.0. Rhododendrons, heathers and azaleas prefer acidic soil with a pH between 4.5 and 6.0, but most flowers grow best between 6.0 and 7.5, slightly acidic to somewhat alkaline. For most plants, nutrients become less available at lower pH levels.

Understanding Lime

• Lime--generally in the form of calcium carbonate--neutralizes acidity and raises the pH. Though some forms are quick acting, they're too caustic to use on a garden. Finely pulverized limestone, the rock formed by the tiny shells of microscopic sea creatures, can be spread across the top of the ground, but it's much more effective when mixed with the soil since its effects move downward very slowly. Dolomite limestone has a high proportion of magnesium, an essential element for plant growth.

Timing Your Applications

• While you certainly can apply lime to a flower garden at any time, the most effective time to do so is in the fall as you prepare the soil for a new bed. Each application will last for four to six years, so there's no need to spread lime on the bed during that time. You can, however, add a bit more lime to the soil whenever you plant a flower that prefers a slightly higher pH, such as lavender or stonecrop. In general, flowers are more adaptable than vegetables. Brassicas such as cabbage and broccoli, for instance, need a nearly neutral pH.

Other Benefits of Lime

• Calcium and magnesium are both essential for plant growth and, though they're adequately supplied in many soils, naturally acidic soil may be deficient. Calcium strengthens cell walls and aids in the transport of other elements. Magnesium activates plant enzymes as well as playing an essential role in photosynthesis. Adding dolomite lime to the soil ensures that both of these nutrients will be well supplied.