Azaleas bloom in the spring (April and May in the temperate Northern Hemisphere, and October and November in the Southern Hemisphere), and their flowers often last several weeks. They are native to several continents including Asia, Europe and North America. Azaleas tolerate shade and prefer to grow near or under trees.
Botanical Note
Rhododendron is the largest genus in the family Ericaceae, with over 1,000 species. Azaleas make up two subgenera of Rhododendron. In the traditional classification, the smaller subgenera Pentanthera and Tsutsusi represent the azaleas. Subgenus Pentanthera holds the deciduous azaleas (23 species, type species R. luteum) and subgenus Tsutsusi the evergreen azaleas (80 species, type species R. indicum). Subgenus Tsutsusi is found in the maritime regions of East Asia (Japan, Korea, Taiwan, East China), but not in North America or Eurasia. Historically, several subgroups of the genus were given generic rank, including Azalea. The name Rhododendron comes from Ancient Greek words meaning "rose" and "tree".
Yellow Azalea
Rhododendron luteum, the yellow azalea or honeysuckle azalea, is a species native to southeastern Europe and southwest Asia. It is a shrub growing 3-4 m tall, with deciduous leaves. The flowers are 3-4 cm in diameter, bright yellow, and strongly perfumed, produced in trusses of 5-25 together. The nectar is toxic because it contains the neurotoxin grayanotoxin. In western Europe the plant is grown as an ornamental and as a rootstock onto which other azalea cultivars are grafted.
Toxicity
Azaleas contain andromedotoxins in both their leaves and nectar, including honey from the nectar. Grayanotoxins are produced by Rhododendron species and other plants in the family Ericaceae. Grayanotoxin I is also known as andromedotoxin. Grayanotoxins are low molecular weight hydrophobic compounds, structurally polyhydroxylated cyclic diterpenes, and their base structure is a 5/7/6/5 ring system that contains no nitrogen. Azalea is dangerous to pets. If a pet eats it, the toxins in the plant tissue can cause central nervous system depression, which in turn can lead to multi-organ failure. Symptoms may include vomiting, diarrhea, seizures, laryngeal edema and heart rhythm disturbances, which can lead to complete cardiac arrest and therefore death.
Cultivation and History
Plant enthusiasts have selectively bred azaleas for hundreds of years, producing thousands of different cultivars. The cultivars are propagated by cuttings, and azalea seeds can also be collected and germinated. Azaleas are generally slow-growing and do best in well-drained acidic soil (4.5-6.0 pH). In the United States, Azalea indica (the group of plants called Southern indicas) was first introduced to the outdoor landscape in the 1830s at the rice plantation Magnolia-on-the-Ashley in Charleston, South Carolina. In Chinese culture, the azalea is known as "thinking of home bush" (sixiang shu). The azalea is also one of the symbols of the city of São Paulo, Brazil.
—
Related: Accord Eudora · African Marigold · Alpha Amylcinnamaldehyde · Alyssum · Angels Trumpet · Aquaflora · Ashoka Flower · Aurantiol
