A number of flowering, broadleaved evergreens, as well as members of the heath family, are identified as ericaceous, indicating a pronounced preference for acid soils, or those with a low pH. Ericaceous plants are called "lime haters." They cannot tolerate chalky or limy soils, nor can they tolerate base soils. If the soil is not sufficiently acid, then ericaceous plants are unable to absorb iron and begin to yellow.
Azaleas are of the heath family and are common garden flowering bushes. Azaleas are evergreens, with dark, shiny leaves that provide year-round foliage, and large, showy blooms in the spring and early summer. Azaleas require excellent drainage in the soil, as their delicate root systems are often destroyed by soggy soils. Azaleas, like other ericaceous flowers will not grow in alkaline or lime-rich soils, such as alluvial or riverbed soil.
Rhododendrons are closely related to azaleas and share many of their growing characteristics. Rhododendrons require large quantities of organic material in the soil, but lime-free composting is essential. According to the University of Missouri, pine bark and leaf mould from pine leaves are the best organic matter to use when growing rhododendrons as they keep soil acid. Peat is to be avoided, as it adds too much moisture to the soil, which can damage roots.
Camellias come in several different varieties. The flowers often appear roselike, and are usually white or light to dark pink. Well-drained soil is essential for healthy camellia growth, as the roots will rot if left standing in water. Camellia leaves yellow and drop due to iron deficiency if they are planted in soils that are too alkaline.
Heather comes in both wild and cultivated forms, typically with mauve or purple blooms, although cultivars have white, pink or red flowers as well. Wild heather flowers can also be seen in many shades of green, coppers and golds. Heather prefers no mulch, and well-drained, acidic soils.
Lily of the Valley
Lilly of the Valley shrub, also called Pieris, or Pieris japonica, is an evergreen shrub that has clusters of tiny, white or cream flowers that hang in bunches that are up to 6 inches long. According to Ohio State University, Lily of the Valley has an "absolute intolerance" to alkaline soils and cannot grow in even pH neutral soil. Like other ericaceous flowers, the Lily of the Valley requires well-drained soil.