Following are some of the European and Asian species and their cultivars you will find in the Azalea Garden at The New York Botanical Garden.
Rhododendron luteum (Pontiac azalea)—Native to Eastern Europe from the Ukraine to Turkey, this azalea is related to R. austrinum (Florida azalea). Found growing along streams and in swamps, the Pontiac azalea usually reaches 4 to 6 feet in height and, ultimately, up to 8 to 10 feet. Its fragrant yellow flowers open in May.
Cultivar: R. ‘Bee Dazzler’, R. ‘Golden Comet’
Rhododendron molle ssp. japonicum (Japanese azalea)—This showy upright azalea grows 4 to 8 feet tall with fragrant, May flowers ranging from yellow to red in color. It foliage turns red in fall.
Rhododendron mucronulatum (Korean azalea/rhododendron)—Classified either as an azalea or deciduous rhododendron, this species is known as a harbinger of spring because its purplish flowers bloom in late March to early April. It grows erect to an average of 6 feet tall and has colorful autumn foliage.
Cultivar: R. ‘Cornell Pink’, R. ‘Crater’s Edge’, R. ‘Easter Bunny’, R. ‘Pink Peignoir’
Rhododendron quinquefolium (five leaf azalea, cork bark azalea)—In its shady, high elevation, mountainous habitat, this azalea grows to 15 feet tall, but in a garden setting it generally stays compact, reaching only 3 to 4 feet. Its whorls of five leaves start out green, become outlined in red and then turn a brilliant red in fall. It has white, pendulous flowers that bloom in early May; the older stems become fissured like cork bark.
Rhododendron schlippenbachii (Royal azalea)—This azalea grows 6 feet tall and wide, forming a globe shape. Its pale- to rose-pink flowers open in early May. Densely branched, its egg-shaped leaves, in whorls of five, will turn colorful in fall if grown in sun.
Rhododendron yedoense var. poukhanense (Korean azalea)—This compact azalea grows 3 to 6 feet tall and equally as wide. It’s lightly fragrant, rose to lilac flowers bloom in early May. The foliage turns orange to red-purple in fall.
Cultivar: R. ‘Rosea’
Rhododendron indicum (sweet indica azalea)—This slow-growing evergreen azalea is often used in creating bonsai. It grows 3 to 6 feet tall and has reddish-purple flowers in late May.
Cultivar: R. ‘Flame Creeper’
Rhododendron kiusianum (Kyushu azalea)—A slow- and low-growing, semi-evergreen with a spreading form, this azalea reaches 3 feet tall and 5 feet wide. Its flowers, in colors of salmon, pink, lavender or white, bloom in late May.
Cultivar: R. ‘Album’
Rhododendron marcrosepalum (big sepal azalea)—Found in well-drained soil in woodlands and open thickets in Japan, this semi-evergreen azalea grows 3 to 6 feet tall. It has hairy leaves and its light, purple-red, fragrant flowers bloom in May.
Rhododendron mucronatum (snow azalea)—This semi-evergreen azalea grows 4 to 6 feet tall with fragrant, pinkish-white flowers that open in May.
Rhododendron nakaharae (dwarf azalea)—This spreading azalea from northern Taiwan, with a maximum height of 1 foot and a spread of 3 to 4 feet, is often used as a groundcover. It prefers sun or part shade over full shade. Its orange-red flowers bloom in late June.
Cultivar: R. ‘Mount Seven Star’
Rhododendron stenopetalum ‘Linearifolium’ (spider azalea)—This semi-evergreen that grows to about 3 feet tall is known for its long, narrow, spidery leaves, which take on a reddish cast in winter. The purple-pink to purple-red flowers echo the form of the foliage. This unusual azalea appeals to collectors and people who like oddities.