There are more than 850 different natural species in the Genus (group) Rhododendron. These wild types, called species (as opposed to hybrids), are native to the temperate regions of Asia, North America, and Europe, as well as to the tropical regions of southeast Asia (specially in Nepal) and northern Australia. None is indigenous to Africa or South America. By far, the largest number of wild species rhododendrons, including the most beautiful of them, are native to Asia. Wild rhododendrons are found from sea level to 19,000 feet in elevation, where they occur in a variety of habitats including alpine regions, coniferous and broadleaved woodlands, temperate rain forests, and even tropical jungle conditions.

Rhododendrons exhibit an enormous diversity of size and shape, from prostrate groundcovers growing no more than a few inches high to trees more than 100 feet tall. Between the prostrate alpine forms and large trees are a variety of shrubby forms in all shapes and sizes. Leaf size ranges from less than 1/4 inch to over three feet long, and also appear in a variety of shapes: rounded, lance-shaped, and elliptical. The flowers may be white, red, pink, yellow, approximate blue, purple, magenta, orange, and in various shades and mixtures of most of these colours. There is diversity, too, in bark texture and colour. And while March, April and May represent the peak months for flowering, some rhododendrons can flower as early as January in an ideal climate, and others as late as August. The actual beauty of many is supreme, in flower, in decorative new growth, in foliage, in bark and in structure, even in fall colour so far as the deciduous azaleas are concerned.