Azaleas
Rhododendrons and Azaleas have long been the go-to plant for northwest gardens. They love it here, so it’s an easy choice.
Plant care & info
Family: Ericaceae
Genus: Rhododendron
Common: Deciduous, Exbury, Mollis, Western, Sweet, Coast Azalea
Eastern & Western North America, Asia & Europe.
All Rhododendrons & Azaleas included in this article lose their leaves during winter. Rhododendron flowers can be white, pink, yellow, orange, red or a combination of several colors. Most are sweetly fragrant. Some flowers are tube-shape, others are funnel-shape and some are double, having extra petals. Bloom time is from late winter to mid spring.
Leaves open with the arrival of flowers or just following bloom. Most are green but some are frosty blue-green and both types display excellent orange, red & purple color before falling in autumn. Some display bronze or red-tinged new leaf growth.
Most grow to around 4-5 feet tall x 5-6’ wide, but can get larger given time.
Unlike their evergreen relatives, deciduous Azaleas and Rhododendrons thrive in full sun. Part-shade to shade is fine too. Plants grown in more shade will have an open airy shape and fewer flowers than plants grown with more light.
Any Rhododendron or Azalea prefers well-drained soil with an acidic pH. The Pacific Northwest naturally has soil with low pH because of copious rain, but much of the area has heavy clay soil, so mixing compost to the bed before planting is advised. Rhodies and Azaleas have shallow root systems and prefer a thin layer of mulch, under 1″.
Fertilizer used should be specific to acid-loving plants, and directions should be followed carefully.
Enemy number one used to be powdery mildew, but now Portland has a pest called Azalea Lace Bug, which sucks chlorophyll from the inside of the foliage, leaving white or coppery stippling.
Most Deciduous Azaleas and Rhododendrons are subject to powdery mildew on leaves during the warmth of summer. It’s a good idea to clean up affected leaves after they’ve fallen off in autumn, and add a light layer of mulch to cover spores that may be laying about on the ground. Options for treatment are many and include:
- Passive acceptance. Powdery Mildew will not (usually) kill the plant.
- Water leaves in the morning. The idea is that the spores that make Powdery Mildew can be washed off. If the leaves are wet during the night, mildew spreads, so allow plenty of time for leaves to dry before nightfall. This is not a fool-proof method, especially considering that rain cannot be controlled, but for those who prefer not to spray, it may be worth a try.
- Chemical warfare. Many fungicides, both organic and synthetic, are available and effective. If you choose to use chemicals, no matter if they are organic or synthetic, be careful to follow the directions carefully and follow all recommended precautions.
The good news is that deciduous azaleas and rhododendrons are not the Lace Bug’s first priority. Azalea Lace Bugs lay their eggs inside the leaves of evergreen azaleas in fall, where they stay protected through the winter and hatch in late spring. Since deciduous azaleas and rhododendrons lose their leaves, they can’t support eggs over winter. Most damage deciduous azaleas receive comes from adult Lace Bugs who have eaten up all the evergreen azaleas in the neighborhood and are moving on to other delicacies.
Read more about Azalea Lace Bug here.
There is a large group of them however that has been overlooked for years; the ones that lose their leaves in winter. Dramatic flower color and sweet perfume, lovely fall leaves and self-sufficiency are some of their best qualities. Plus they thrive in sunshine while their evergreen relatives burn.
Many of the plants listed below were bred from Azaleas that are native to the United States. Knapp Hill Nursery, Goldsworth Old Nursery and Exbury began to hybridize in the late 1800s using Rhododendron calendulaceum and Rhododendron arborescens (both native to eastern U.S.), Rhododendron occidentale (native to the Pacific Northwest), and Rhododendron molle (native to China). Many of their hybrids are still sold today. Locally, Ivan and Robertha Arneson used those hybrids to breed new Azaleas into the 1990’s. Arneson Azlaeas are now some of the best and most popular on the market.
The Difference between Azaleas and Rhododendrons
- All Azaleas are members of the genus Rhododendron.
- Deciduous Azaleas are in the subgenus Pentanthera,
- Evergreen Azaleas are in the subgenus Tsustusti.
- All Azaleas are elepidotes; they never have scales on the bottom side of their leaves.
- Azaleas one stamen per flower lobe – Rhododendrons have two stamens per lobe.
- Azaleas have hairs on their leaves that grow parallel to the leaf surface.
The Crystal Springs Rhododendron Garden near Reed College is a wonderful place to see deciduous rhododendrons in bloom in spring.
Explore More Azalea
Azalea 'Arneson Gem'
Azalea ‘Arneson Gem’
Red flower buds open to yellow-orange flowers w/ red edges, disease resistant leaves, maroon color in autumn. Grows to 3’ x 4’. Zone 5.
Azalea 'Cannon’s Double'
Azalea ‘Cannon’s Double’
Cream, gold and pink double(many petals) flowers. New leaves have a bronze cast & turn green in summer. Upright, open & airy growth to 5’ x 6’. Hardy Z5.
Azalea 'Fragrant Star'
Azalea ‘Fragrant Star’
Slender & elegant white flowers with intense sweet fragrance and frosty blue-green leaves that turn orange and red in fall. Grows to 4’ x 4’. Hardy Zone 5.
Azalea 'Gibraltar'
Azalea ‘Gibraltar’
Red flower buds, deep orange flowers w/ gold tinge on the upper lobe. Leaves are mildew resistant. Grows to 4’ x 4’.
Azalea 'Klondyke'
Azalea ‘Klondyke’
Orange flower buds open to gold flowers. New leaves are tinged with bronze and turn green in summer. Grows to 4-6’ tall, 3-5’ wide, Zone 5.
Azalea 'Mandarin Lights'
Azalea ‘Mandarin Lights’
Red-orange flower buds open to only slightly lighter orange flowers. Grows to 5’ x 4’. The ‘Lights’ series is more cold tolerant than other Deciduous Azaleas, hardy to Zone 4.
Azalea 'Northern Hi-Lights'
Azalea ‘Northern Hi-Lights’
White flowers with a strong yellow blotch on the upper petal. Blooms at the same time that leaves appear, a bit later than others. Grows to 4’ x 3-4’, Hardy to Z4.
Rhododendron Occidentale: Western Azalea
Rhododendron Occidentale: Western Azalea
Native to Oregon and California coastal areas – Flower color varies on plants found in the wild, or in plants grown from seeds. White, pale pink, yellow to orange or combinations of all of these colors are common. Flowers have a sweet honeysuckle-like scent and bloom in mid April to early May. Leaves are green and turn yellow, orange and red in fall. Growth is more compact than many other deciduous Azaleas, to about 3-5’ with a more dense shape. Hardy to -5f.
