Literally translated from Japanese words that mean "fifth moon," Satsuki azaleas are evergreen azaleas that usually grow 2 to 4, sometimes 6 feet tall and equally as wide. "Fifth moon" refers to the fifth lunar month of the traditional oriental calender, in honor of the month when these shrubs begin to open the large flowers. They are appropriate for growing in USDA winter hardiness zones 7 through 9, keeping in mind they do need some chilling winter temperatures to produce flowers in springtime.
Satsuki azaleas are the result of hybridizing two species of evergreen azaleas, Rhododedron indicum and dwarf-sized Rhododendron eriocarpum (formerly known as Rhododendron tamurae). It is believed these two species naturally crossed in Japan and gained favor by locals as superb ornamental shrubs.
Satsuki azaleas were bred and grown in Japan at least since the 16th century. Westerners learned of them as Japan became less isolated in the 19th century. Satsuki azaleas were first brought into the United States and enjoyed by gardeners in the 1930s.
Scores of different varieties (cultivars) of Satsuki azaleas exist today. Their flowers are the primary distinguishing characteristics among them, although mature plant form is also a key feature. Although few solid-colored varieties are known within this group of azaleas, most have random picturesque streaks, blotches or speckles of a second color on their flower petals. Blossoms may carry and combination of white, red, purple, pink, pale pink, hot pink, rose, salmon, or coral. Look for varieties with Japanese names such as 'Izayoi', 'Ariake-no-tsuki', 'Kaisen', 'Onyo', 'Kagetsu-no-homare', 'Gakurei', 'Kako', 'Tatsumi-no-hikari', 'Datemurasaki' and 'Tanima-no-yuki'. Anglican names also exist on some varieties (such as 'Geisha Girl', 'Gumpo Pink' and 'Gumpo White'), but plant labels and breeders do specify if they indeed are considered a Satsuki azalea type.
Plant Satsuki azaleas in a moist, humus-rich acidic soil that is fertile--sand and loam types are ideal as long as they have good drainage. Although the soil must remain moist over the chilly winter months, do not allow over-watering to encourage root rot at this time. Plant these azaleas in partially shaded locations so they receive either very bright indirect light or dapple sun rays through overhead trees.
According to the Satsuki Azalea Society, in early spring, lightly fertilize shrubs until they begin showing their flower buds, and then stop fertilizing until the flowering season ends. New growth of the shrubs occurs in June and July when fertilizing can occur, but growth stops and the leaves and stems mature in August and September as days shorten and cool nights begin in autumn. Too much winter cold can cause the evergreen leaves to scald and drop away. Do not plant them in cold, windy locations.
Satsuki azaleas have traditionally been used as evergreen bonsai specimens. Even if not rigorously maintained by pruning as bonsai, these azaleas grow well in containers for display anywhere in the garden. They also are nice shrubs for woodland gardens and since they bloom later in spring they can be used to provide floral color to bridge the gap between early spring-blooming deciduous azaleas, mid-spring large rhododendron shrubs and some of the summer-flowering North American azaleas.