The genus, Rhododendron, has over 900 different species and probably 10,000 named cultivars. They range in size from a few inches tall to giants reaching 80 feet in the air. There are both deciduous and evergreen rhododendrons. Most commonly, their flowers are in shades of white, pink, red, lavender, or purple and various bicolor types.

A point of confusion often arises over the term azalea. Azaleas are all in the genus, Rhododendron. Experts debate over what defines and azalea as separate from rhododendrons. Some look at the number of stamens in the flowers but I use a simpler classification. To me, azaleas are rhododendrons that bear flowers all along the stem while rhododendrons bear their flowers at the terminal end of branches. Again, there are both deciduous and evergreen plants in both category of rhododendrons.

Members of this genus tend to have exacting requirements in terms of site, soil and climate.

These are upright shrubs that grow up to 6 feet or more. Most of the cultivars bloom in late May to early June or, in some cases, even later into summer.

Plants in this group have 5 stamens in their flowers and belong to the Pentathera Section of rhododendrons. They produce flowers just before or as the new leaves open. Many of the common cultivars have trusses of orange or red flowers. The new foliage is often reddish colored also.

Some of the more popular deciduous azaleas belong to the Knap Hill collection or are Rhododendron x 'Exbury Hybrids'. Knap Hill is a famous nursery in Surrey, England from the early 20th century. Exbury Gardens in Southhampton, Hampshire, England, continued the breeding based of deciduous azaleas. The basis for the hybrids is a cross between Chinese and American species of azaleas such as R. calendulaceum, R. viscosum and R. arborescens.

Based on certain hybrids from Belgium and the Weston Hybrids from the United States, the Ghent Hybrids represent another group of deciduous azaleas. These tend to be smaller plants with fragrant flowers. They are also very cold hardy withstanding temperatures in the -25 degrees F.

 These tend to be very prolific bloomers and some have so many flowers that they completely cover the evergreen foliage. Evergreen azaleas are noted as being more shade tolerant that the deciduous types although more sun will promote better flowering. Many of them have good quality fall color too.