Garden lime reduces the acidity found in some soils. It enables plants to take up the nutrients they need for healthy growth.
Plants can't get the nutrients that they need to develop if the soil is too acidic. Garden lime is also a valuable source of calcium.
The pH level is a number that describes how acid or alkaline a soil is and from this it is calculated how much lime is needed to reduce acidity.
The pH scale goes from 0 to 14, 0 being very acidic, 7 being neutral and 14 very alkaline. Most soils are between 4 and 9 pH. It's best to have a pH somewhere in the middle. Between 6 and 7 is generally considered idea. If your soil pH is 5.5 it would be advisable to add lime to raise the pH level.
You can test your soil pH yourself using a DIY kit widely available at garden centres. These kits are relatively cheap and easy to use and give a good indication of soil pH.
Garden lime can be applied throughout the year, but for best results use in autumn before winter and the first frosts. For normal (neutral) soils use garden lime every third year. Highly acidic soils may need an annual application.
Garden lime should only be used only where there is a recognised need. Do not exceed the appropriate application rate. Increasing the dosage may result in damage to plants.
Apply evenly around plants and avoid spillage onto foliage or plant stems.
Do not apply around ericaceous (lime hating) plants and vegetables e.g. Rhododendron, Azaleas, Camelia and Heather.
Children and pets can continue to use treated areas immediately after application.
More information can be found on the RHS website.