ERICACEAE, The Heath family
Deciduous azaleas are one of the unexpected treats of fall color in Portland. Many shrubs that in the Midwest would lose their leaves so quickly one might not notice any color, go more gently here and put on a show as they depart- Deutzia, spirea, viburnum and dogwoods among them. It’s not the ‘wow’ factor of a whole hillside aflame with sugar maples, but the seasonal delights for color worshipers here are subtle and varied.
Rhododendrons and azaleas are in the same genus. Among the azaleas there are evergreen and deciduous, and many groups of each. The deciduous are generally taller plants with larger flowers that come in white, red, pink, coral, fuchsia, orange, lavender and bicolor. There are deciduous azaleas far hardier than their evergreen relatives.
Some of the deciduous groups are the Knap Hill-Exbury hybrids, developed in England and the parents of azaleas in the Arneson and Ilam hybrids. These are hardy to around -20 F. The Western Azalea, R. occidentale is native to California and Oregon. R. vaseyi and R. viscosum from North Carolina, are very fragrant and have been crossed with crosses of Japanese species (R. japonicum) to produced brightly colored, clove-scented blossoms. There are also fragrant species from Korea and China called Royal azaleas.
The hardies azaleas (to -45 F) are the Northern Lights series, bred by the University of Minnesota. They are also, in my opinion, the most beautiful. They bloom late, which is a good attribute in cold climates where late frost is a blossom killer. The first in the series was introduced in 1978. An additional dozen have been released, including ‘Lemon Lights’, ‘Orchid Lights’, ‘Pink Lights’, ‘Golden Lights’, ‘Rosy Lights’ and ‘White Lights’. Some are bi-color, resistant to mildew, or fragrant, and all have sterile flowers so there is no need to deadhead. The shrubs vary in height from 4 to 10 feet tall and like full sun except in hot climates. They require moist, acidic, well-drained soil and mulch in summer.