Azaleas and rhododendrons are two of the most celebrated shrubs in the gardening world. With more similarities than differences, it’s easy to confuse the two. By learning how they are different, you can choose the best shrub for your yard, take care of their specific needs, and gain a greater appreciation for the many beautiful types of shrubs that are out there.
Both of these species come from the larger rhododendron genus, which explains their close similarities. In that sense, you can say that azaleas are a type of rhododendron. Look at the botanical name of azaleas, and you’ll even find the genus rhododendron. But when most gardeners say “rhododendrons,” they’re not talking about the whole genus. They’re talking about a certain type of shrub that is also called a rhododendron but is not the same as an azalea.
Azaleas and rhododendrons are two types of ornamental shrubs that belong to the genus Rhododendron. While they are closely related and have similar growing requirements, there are some key differences between azaleas and rhododendrons.
An Overview of Azaleas
Azaleas are deciduous or evergreen flowering shrubs that belong to the Rhododendron genus There are over 10,000 cultivars, with sizes ranging from compact dwarf varieties to large shrubs reaching over 15 feet tall
Azaleas produce an abundance of colorful spring blooms. Flower colors include shades of pink, purple red orange, yellow and white. The flowers have 5 stamens and a narrow, tubular or funnel shape. Each flower stem has only one bloom.
Most azaleas are native to North America, particularly the southeastern United States. They thrive in mildly acidic, organically rich, well-drained soil and prefer partial shade. Pruning should be done right after flowering to avoid removing next year’s flower buds.
Popular azalea varieties include:
- Encore® – Reblooming hybrids in various colors
- Exbury – Deciduous hybrids with large, colorful blooms
- Satsuki – Evergreen Japanese azaleas with frilly flowers
- Kurume – Evergreen hybrids from Japan with bright, bold blooms
An Overview of Rhododendrons
Rhododendrons are evergreen shrubs with large, leathery leaves. There are over 1,000 species, ranging from dwarf varieties to large shrubs and small trees up to 20 feet tall.
Rhododendrons produce colorful blooms in late spring to early summer. The flower colors include white, pink, red, purple and yellow. The blooms have a bell shape with 10 stamens and appear in dense, showy clusters at the ends of branches.
Rhododendrons thrive in cool climates and prefer acidic, organically enriched soil. They require consistent moisture and afternoon shade in hotter zones. Deadheading spent blooms and removing dead wood keeps plants looking their best.
Some popular rhododendron varieties include:
- Catawba – Very hardy with purple flowers
- English Roseum – Profuse pink blooms in early summer
- Nova Zembla – Red flowers on a compact shrub
- Roseum Elegans – Fast growing with pink blooms
Key Differences Between Azaleas and Rhododendrons
While azaleas and rhododendrons are in the same genus, there are some notable differences between these flowering shrubs:
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Bloom season – Azaleas bloom in spring, while rhododendrons bloom in late spring into early summer.
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Flowers – Azaleas have tubular or funnel-shaped flowers with 5 stamens. Rhododendrons have bell-shaped blooms with 10 stamens.
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Bloom formation – Azaleas produce 1 flower per stem, creating a blanket of color. Rhododendrons have large clusters of blooms at the ends of branches.
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Flower colors – Azaleas come in a wide range of colors including yellow. Rhododendron blooms are rarely yellow.
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Leaves – Azaleas have smooth, thin leaves. Rhododendron leaves are large, leathery and often have scaly undersides.
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Scent – Some azaleas are fragrant, while most rhododendrons have little or no scent.
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Plant size – Azaleas range hugely in size. Rhododendrons are typically large, dense shrubs.
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Climate – Azaleas tolerate more heat and sun. Rhododendrons prefer cooler conditions.
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Hardiness – Evergreen azaleas are hardy to zone 6, while deciduous azaleas can grow in zone 4. Most rhododendrons need zone 5 or warmer.
Similarities Between Azaleas and Rhododendrons
While they have some distinct differences, azaleas and rhododendrons do share the following similarities:
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They are members of the Ericaceae family.
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Both plants prefer well-drained, acidic soil rich in organic matter.
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Azaleas and rhododendrons thrive in partial or filtered shade.
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Neither plant tolerates soggy soil or poor drainage.
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Mulching helps keep roots cool and maintain soil moisture for both shrubs.
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Fertilizing with acid-based plant foods formulated for azaleas/rhododendrons keeps plants lush.
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Insect pests like lace bugs, mites and scale may affect both plants.
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Pruning should be done immediately after flowering to preserve next year’s blooms.
Tips for Planting Azaleas and Rhododendrons
Here are some tips to ensure success when adding azaleas and rhododendrons to your landscape:
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Select a part-shade location with morning sun and afternoon shade.
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Prepare the planting area well in advance by working in pine bark fines, peat moss or leaf mold to amend and acidify soil.
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Space plants properly to allow for mature size – small varieties 2-3 feet apart and large shrubs 5-6 feet apart.
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Plant the top of the root ball even with the soil surface and water deeply after planting.
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Apply 2-4 inches of pine needle or bark mulch around plants, keeping it a few inches from the stems.
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Water thoroughly during the first growing season to help establish an extensive root system.
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Fertilize in early spring with an acid-based fertilizer formulated for azaleas and rhododendrons.
The Takeaway
While azaleas and rhododendrons are close cousins and have very similar needs, there are notable differences between these two flowering shrubs. Paying attention to bloom time, flower characteristics and plant size will help you select the right shrub for your landscape needs. Proper planting and care will keep azaleas and rhododendrons thriving for years of beauty.
Azaleas vs. Rhododendrons: The Main Differences
Below are some details that can allow you to identify and distinguish these shrubs:
- Shape of the Flower: Rhododendron flowers are usually bell-shaped, while azalea flowers are tubular or trumpet-shaped.
- Number of Stamens: Azalea flowers have five to six stamens, while rhododendron flowers have ten.
- Flower Clusters: Rhododendrons have groups of flowers, while azalea flowers are on single stems but look like they’re in a group because they’re close together.
- Color of the Flower: Azaleas usually have a wider range of colors, from white to red, orange, yellow, cream, purple, pink, and everything in between. Rhododendrons, on the other hand, come in more traditional colors like white, pink, purple, red, and sometimes yellow.
- Type of Leaves: Azaleas usually lose their leaves in the fall, but in some climates, they may stay green all winter. In contrast, rhododendrons are mostly evergreens.
- Rhododendrons have bigger, thicker, leathery, paddle-shaped leaves, while azaleas’ leaves are usually small, thin, oval-shaped, or pointed.
- When They Bloom: Azaleas usually bloom in April, but some “repeat blooming” types bloom again in the summer. Most rhododendrons bloom later in the spring, after azaleas.
Common Features of Azaleas and Rhododendrons
Even though they are slightly different, both groups of shrubs have lots of colorful flowers in the spring that will make your yard look beautiful. Both personalities are beautiful, classy, and full of color. It’s not often that evergreen shrubs like many rhododendrons and some azaleas have such amazing blooms. The deciduous varieties are no less stunning.
What’s the difference between Azaleas and Rhododendrons – Plant Identification Guide
FAQ
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