Extremely hardy azaleas are unusual. Here are the hardy dwarf azaleas.

Hino-red, -20F. Flower openly funnel-shaped, 1.5" across, moderate red. Inflorescence 3-flowered. Leaves to 1.5" long, mid green. Spreading, dense habit. Grows twice as wide as tall. Grows twice as wide as tall. 1 ft tall in 10 years.

Hino-white, -20F. Flower single, 1.5" to 2" across, white, unmarked. Inflorescence 3-flowered. Leaves 1âÂÂ" to 1.5" long, olive green. Spreading, dense habit. Grows twice as wide as tall. 1 ft tall in 10 years.

Bixby, -20F. Flower openly funnel-shaped, wavy edges, 1.5" across, red, unmarked. Flatted dome-shaped inflorescence with 3 flowers. Leaves obovate, mucronate apex, cuneate base, 1.5" long, concave, bullate, retained for 2 years. Dense, compact growth habit. 2 ft tall in 10 years.

Helen Curtis, -20F. Flower widely funnel-shaped, frilly, about 2.5" across, semi-double, white, unmarked. Inflorescence 2-3 flowered. Leaves broadly elliptic, acute apex, rounded base, 1.5" long, glossy, yellow-green, retained for 2 years. Upright, rounded habit. 2 ft tall in 10 years.

Marie's Choice, -20F. Flower openly funnel-shaped, frilly-edges, 3" across, fragrant, white, unmarked. Inflorescence 2-3 flowered. Leaves near elliptic to near narrowly obovate, convex, mucronate apex, cuneate base, glossy, yellow green, 1 3/4" long, retained 2 years. Upright, broad habit. 2 ft tall in 10 years.

The following are species, but they are only hardy to Zone 6, -10F.

R. kiusianum (dwarf azalea) and R. nakaharai (dwarf azalea) are both dwarf azaleas.

R. kiusianum blooms while still young, bearing white, pink, rose or purple flowers 1 to 1 1/2 inches across. The shiny 1-inch leaves sometimes turn red in winter. This open, twiggy plant grows slowly to 3 feet tall and 5 feet wide.

R. nakaharai forms a low dense mound that seems to grow flatter as it matures, since its ultimate height is 6 to 9 inches, while its spread is 12 to 15 inches. The small, shiny leaves, 2 inches long, are hairy on the undersides. The 3-inch pink, salmon or red flowers are saucer shaped and, unlike most azaleas, open in midsummer.