How to Easily Spot the Difference Between Azalea vs. Rhododendron Flowers
The Spruce / Evgeniya Vlasova
Is it a rhododendron or an azalea? It can be puzzling because all azaleas are rhododendrons, but not all rhododendrons are azaleas.
Both plants are woody, rounded shrubs in the Ericaceae (blueberry) family with many cultivars and varieties. Growing requirements, depending on the cultivar, for rhododendrons and azaleas are the same.
To help you determine which is which, here are the main differences:
Most azaleas bloom in early spring, while rhododendrons bloom in June.
Azaleas have tubular-shaped blooms with five stamens. Rhododendrons have bell-shaped blooms with 10 stamens.
Azaleas have one flower per stem, and rhododendrons have clustered blooms at the end of each stem
Azalea blooms can be white, cream, pink, purple, orange, or yellow—rhododendron blooms are rarely yellow
Read on to learn more about these similar plants.
What Are Azaleas?
There are more than 10,000 different varieties of azaleas and all belong to the genus Rhododendron, which is why the flowers often get confused for one another.
Native North American azaleas are deciduous, meaning they shed their leaves in the fall. Flowers are typically smaller than hybrids and appear in the spring with colors ranging from white to purple, pink, red, orange, and yellow.
The woody shrubs vary from stiffly upright to broad spreading, from rounded to irregular, from dense and compact to open and tree-like. Height can range from under a foot to well over 15 feet.
Azaleas are relatively pest-free and are easy to grow. They prefer to be planted in acidic, well-draining soil in cool, partially shaded sites, away from drying winds. Organic matter worked into the soil before planting will usually provide sufficient nutrients for adequate growth.
Pruning should be done immediately after they bloom to avoid cutting off next year’s flower buds, and dead wood can be removed at any time. Yellowing leaves show a lack of iron which is essential for healthy azaleas. Application of an iron solution as a foliage spray should be applied during the growing season.
Types of Azaleas
'Coral Bells' (Rhododendron indicum 'Coral Bells'): An evergreen azalea with showy pink flowers that appear in the spring. It grows at a medium pace to a height of two to six feet and a width of three to six feet.
'Golden Oriole' (Rhododendron 'Golden Oriole'): A deciduous azalea with yellow-orange flowers growing six ft. tall by four to six ft. wide.
‘Ramapo’ (Rhododendron ‘Ramapo’): A compact evergreen azalea growing one to three feet tall and two to four feet with blue, yellow, pink, purple, lavender, or white blooms.
Alabama Azalea (Rhododendron alabamense): Native to Alabama and Georgia, this compact rhododendron grows to a height and width of four to six feet. It has white flowers with a prominent lemon-yellow blotch on the upper petal, and a distinct, lemon fragrance.
Flame Azalea (Rhododendron calendulaceum): An upright, woody, deciduous azalea, it typically matures to four to eight feet tall and eight to 10 feet wide. The common name of flame azalea is about the resemblance of the upright fiery red-orange flower buds to candle flames.
Korean Azalea (Rhododendron mucronulatum): A woody, open-growth, deciduous azalea, it grows at a relatively slow rate to four to eight feet tall and wide. Varieties include 'Cornell Pink' and 'Mahogany Red'.
Encore® Azalea (Rhododendron 'Encore'): A hybrid, re-blooming azalea available in 33 varieties of bloom colors and sizes.
What Are Rhododendrons?
Rhododendrons are small trees in the Ericaceae family with large clusters of bell-shaped flowers and large evergreen leaves.
In the nursery trade, rhododendrons are sold as an entirely different plant than an azalea (which is classified as a Rhododendron). Some varieties are compact while others resemble trees. Sizes range from five to 20 feet or more.
Rhododendrons are native to North America, Asia, and Europe and there are thousands of hybrids. The blooms appear in clusters at the end of the branch and are typically white, pink, purple, and red with five lobes per flower and 10 stamens. The leaves are deep green elliptic, thick, leathery, and glossy. The undersides may be scaly or have small raised dots. Fruit appears in the fall at the end of the branches as a cluster of dried red-brown capsules, 1/2" long that release seeds.
Like azaleas, they prefer to be planted in filtered shade in well-draining, acidic soil (4.5 to 6.0 pH). As shallow-rooted plants, they require irrigation during dry periods. This can be aided by mulching the plant at least four inches deep to help preserve moisture.
Rhododendrons like to be deadheaded, removing dead flowers to prevent the development of seeds that zap the plant's energy. Disbudding, or pinching out the terminal leaf bud on new growth, awakens dormant buds and causes side branches to appear. Disbudding is done on new growth and can be done again in the fall.
A few common insect problems are lace bugs, mites, and scale.
Types of Rhododendron
'Dr. A. Blok' (Rhododendron 'Dr. A. Blok'): Hybrid with pink flowers reaching a maximum height and width of 7 feet.
Carolina rhododendron (R. carolinianum): Three to six feet tall with a similar spread. Late bloomer with pale lilac flowers. One of the hardiest native evergreen rhododendrons.
Catawba rhododendron (R. catawbiense): Four to six feet tall with a wide, loose spread. Lilac-magenta flowers late in the season. The plant is known for its extreme hardiness and as the parent of most hardy hybrids.
‘Ginny Gee’ (R, ‘Ginny Gee’): Grows only to two feet. Produces abundant pink to white flowers.
‘Lee’s Dark Purple’ (R. ‘Lee’s Dark Purple’): Grows to six feet with late-season dark purple flowers.
‘Roseum Elegans’ (R. ‘Roseum Elegans’): Vigorous, fast-growing plant reaching six feet with rosy-lilac blooms. Extremely heat tolerant.
‘Vulcan’s Flame’ (R. ‘Vulcan’s Flame’): Heat-resistant plant with bright red flowers that appear in midseason.
Key Differences Between Azaleas and Rhododendrons
Growth Habits
Azalea vary in growth habits depending on the variety. Some are dense and rounded, while others are open and upright. Mature growth can range from under a foot to well over 15 feet. Rhododendron varieties range from small hybrids to large tree forms that reach heights of five to 20 feet.
Leaf Characteristics
Azaleas can be evergreen or deciduous, and their leaves are elliptical to obovate in shape, small, and thin. The back side of the leaves is smooth.
Rhododendrons are typically evergreen with deep green, thick leaves that are leathery and glossy. The undersides may feel slightly fuzzy, scaly, or have small raised dots.
Flower Characteristics
Azalea blooms are funnel-shaped with five stamens. Native azalea blooms are usually small and the white, purple, pink, red, orange, or yellow flowers appear in early spring and yellow. Evergreen azaleas produce white, various shades of purple, pink, red, or reddish-orange flowers in the spring. The hybrid Encore® azaleas bloom in the spring and rebloom in the summer and fall.
Rhododendron flowers are larger, bell-shaped, and have 10 stamens. Most varieties bloom in June with the flowers appearing as clusters at the end of the branch. Rhododendron blooms are typically white, pink, purple, and red.
Climate Adaptability
Due to the hybridization of azaleas, there are varieties suitable for USDA Hardiness Zones 6a - 9b. While there are some heat-tolerant varieties of rhododendron, most prefer cooler temperatures and are best planted in USDA Hardiness Zones 4a-8b.
Similarities Between Azaleas and Rhododendrons
Both plants are woody shrubs that prefer filtered shade, away from drying winds. Optimum growth and flower production will happen in well-draining, acidic (4.5 to 6.0 pH) soil. Both plants should be mulched well to help keep the roots cool.
Read Next: Add One of These 21 Pretty Flowers That Look Like Roses to Your Garden
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