Rhododendron calendulaceum

It is a deciduous shrub, 120–450 cm tall. The leaves are simple, 3–7 cm long, slightly dull green above and villous below. The arrangement is generally alternate, however they appear whorled towards the tips of the branches.

The flowers are 4–5 cm long, usually bright orange, but can vary from pastel orange to dark reddish-orange. These non-fragrant flowers have 4-5 lobes and grow in clusters of 5-10. It typically blooms in late May and early June.[3][4]

This species of Rhododendron is native to the Appalachian Mountains in the eastern United States, ranging from southern Pennsylvania and Ohio to northern Georgia. It has been reported historically in New York and Maryland, however its current native status in these states is undetermined.[5] However, it can occur as an introduced species in anthropogenic habitats. It occurs naturally in mixed deciduous forests.

The flame azalea is a popular cultivated plant, primarily due to its showy flowers. Many cultivars and domestic varieties exist, including:

• Chattooga
• Cherokee
• Golden Sunset Flame
• Golden Yellow Flame
• Smokey Mountaineer
• Wahsega[4]

It is also an important parent species in hybrid Azaleas, such as:

• Ghent
• Knap Hill
• Maid in the Shade
• Mollis
• Northern Lights[6]

• 
  'Mandarin Red' Flowers (cultivar)
• 
  Rhododendron calendulaceumby Ellis Rowan, 1901

• Central and southern Appalachian montane oak forest

• North Carolina State University