The vivid displays produced by rhododendrons and azaleas can last from spring into summer. There are plants to fit any size garden, but the soil must be right. The value of this group of plants for the home landscape can hardly be overestimated. Ranging from matlike dwarf shrubs only a few inches high to trees more than 40 feet tall, rhododendrons and azaleas offer a remarkable variety of sizes and shapes.

Most rhododendrons have magnificent foliage, and the flowers of many varieties are among the most beautiful in the world of shrubs. The flowers' colors are white, lavender, violet, purple, pink, crimson, scarlet, orange and yellow. Their shapes are tubular, starry, funnel- or bowl-shaped, and bell-like, varying in size from 3/4 to 6 inches wide and from 3/4 to 4 inches long. The flowers are usually produced in rounded trusses with as many as 15 individual blossoms on each one.

Rhododendrons and azaleas grow beautifully in dappled sunlight or partial shade and in moist, acid soil. They also do quite well in full sunlight, but flowers last longer with some shade. They will not survive in alkaline soil or in hot, dry situations. These plants have a remarkable range of hardiness. Gardeners in even the coldest climates can enjoy at least a few of these attractive shrubs.

The rhododendron is derived from the Greek words "rhodon", which means rose, and "dendron", which means tree. When the traditional large-leaved rhododendrons are in bloom, they fully live up to the promise of their name.

The first species made available for garden use, in the mid 1600's, was Rhododendron hirusutum, native to the mountains of Europe. In 1753 the Swedish botanist Linnaeus officially established and named the genus Rhododendron. At the same time he created the separate genus Azalea. Then, in the 19th century, another botanist, George Don, discovered that there was little botanical difference between the two, and they were both classified as the genus Rhododendron, which they remain to this day. Gardeners still prefer to talk of rhododendrons and azaleas as separate kinds of plants, and they are so identified in nurseries and catalogs.

There are deciduous and evergreen species of both kinds. The evergreens are the most popular, but there is an increasing interest in deciduous azaleas. Few deciduous rhododendrons are grown. Rhododendrons occur in the wild all over the world. Most hybrids have been developed from species native to Burma, China and northern India. Many of these were crossed with a native American species, which grow wild in the mountains from Virginia to Georgia.

The more resistant these plants are to cold weather, the more resistant it will also be to heat. Therefore, to grow rhododendrons and azaleas in a warmer climate than is usually recommended, it is best to choose the hardiest varieties.