This refers to plants, such as heather, pieris, rhododendron, camellia and vaccinium, which all like acid soil. These plants are also known as lime-hating or calcifuge plants.
Lime or chalk in the soil will often turn the leaves of ericaceous plants yellow and they may even die. They are best grown in peaty, lime-free soils. If your soil does contain lime, you can still grow them in containers or beds filled with lime-free, ericaceous compost.