What is the Difference Between Azalea and Rhododendron

Azalea and rhododendron are two types of flowering shrubs. They are two of the most celebrated shrubs in the gardening world. Both of these species come from the larger Rhododendron genus. Often, people confuse them as they have more similarities than differences.

The key difference between azalea and rhododendron is their appearance. Azalea is a small to medium-sized flowering shrub with many smaller stems, while rhododendron is a larger flowering shrub with fewer stout stems.

CONTENTS

1. Overview and Key Difference
2. What is Azalea 
3. What is Rhododendron
4. Similarities – Azalea and Rhododendron
5. Azalea vs Rhododendron in Tabular Form
6. Summary – Azalea vs Rhododendron
7. FAQ – Azalea and Rhododendron

What is Azalea?

Azalea is a member of the Rhododendron genus. Azaleas are native to several continents, including Asia, Europe and North America. An azalea is not typically evergreen; it is usually deciduous. It is a small- to medium-sized flowering shrub with numerous smaller stems. It has tubular or trumpet-shaped flowers. Azalea flowers typically have only 5 projecting stamens. These flowers are each attached to single stems.

Figure 01: Azalea

Azalea has a wider variety of colours, ranging from white to red, orange, yellow, cream, purple, pink, and anything in between. Azaleas usually have small, thin, oval-shaped, or pointed leaves. They usually bloom in April, but some varieties have a second bloom time in the summer.

What is Rhododendron?

Rhododendron is an evergreen flowering shrub native to the temperate regions of Asia, North America, and Europe, as well as the tropical regions of Southeast Asia and northern Australia. Rhododendron usually has bell-shaped flowers.

Figure 02: Rhododendron

Rhododendron flowers have ten stamens, and this flowering shrub features clusters of flowers. The colors of rhododendrons typically include a classic palette of white, pink, purple, red, and occasionally yellow. Moreover, rhododendrons normally have larger, thicker, leathery, paddle-shaped leaves. In addition to that, the blooming time of most rhododendrons is late spring, after azaleas.

Similarities Between Azalea and Rhododendron

1. Azalea and rhododendron are two types of flowering shrubs.
2. Both these shrubs belong to the larger Rhododendron genus.
3. Both these shrubs can be evergreens.
4. They are very popular in the garden world.

Difference Between Azalea and Rhododendron

Definition

1. Azalea is a small to medium-sized flowering shrub with many smaller stems in the genus Rhododendron.
2. Rhododendron is a larger flowering shrub with fewer stout stems in the genus of Rhododendron.

Abundant in

1. Azalea is a shrub native to several continents, including Asia, Europe, and North America.
2. Rhododendron is a shrub native to the temperate regions of Asia, North America, and Europe, as well as to the tropical regions of Southeast Asia and northern Australia.

Flower Morphology

1. Azalea has tubular or trumpet-shaped flowers and 5 stamens.
2. Rhododendron is usually have bell-shaped flowers and 10 stamens.

Flower Colour

1. Azalea has a wider variety of colours which including white to red, orange, yellow, cream, purple, pink, and anything in between.
2. Rhododendron has a wider variety of colours which including classic palette of white, pink, purple, red, and sometimes yellow.

Types of Leaves

1. Azaleas are usually deciduous but may be evergreen based on climate.
2. Rhododendrons are mostly evergreens.

Leaves Shape

1. Azaleas have small, thin, oval-shaped, or pointed leaves.
2. Rhododendrons have larger, thicker, leathery, paddle-shaped leaves.

Blooming Time

1. Azaleas usually bloom in April, but sometimes they have a second bloom time in the summer.
2. Rhododendrons usually bloom in late spring, after azaleas.

Diseases and Pathogens Affecting the Plant

1. Azalea bark scale, azalea lace bug, azalea caterpillars, azalea leafminer, and azalea whitefly commonly affect the azaleas.
2. Rhododendron borer and rhododendron stem borer commonly affect rhododendrons.

Summary – Azalea vs Rhododendron

Rhododendron is a very large genus.  It has about 1,024 species of woody plants. Azalea and rhododendron are two types of flowering shrubs that belong to the Rhododendron genus. Both these flowering shrubs may have similar features, which can make it challenging for gardeners to distinguish them from each other. However, azalea is a small to medium-sized flowering shrub with many smaller stems, while rhododendron is a larger flowering shrub with fewer stout stems. Moreover, azaleas mainly bloom in April, whereas rhododendrons normally bloom in late spring after azaleas. This summarizes the difference between azalea and rhododendron.

FAQ: Azalea and Rhododendron

1. Where are azaleas found?

• The majority of azaleas are native to North America. All of the North American natives are deciduous and tend to have open, loosely branched habits. They are known for their hardiness and exquisite fall foliage.

2. Where do azaleas grow best?

• Azaleas are well-grown in locations that experience morning sun and afternoon shade or filtered light. Exposure to hot all-day sun can stress the plants and make them more susceptible to pests. Azaleas also require humus-rich, well-drained, acidic soil.

3. Are azaleas hard to keep alive?

• Azaleas tend to struggle when grown near house foundations. This is often due to compacted, alkaline soil, drought, poor drainage, reduced airflow, and reflected heat from the walls. Additionally, excessive sunlight can hinder their growth.

4. Where are Rhododendrons found?

• Most species of rhododendrons are native to eastern Asia and the Himalayan region, but smaller numbers occur elsewhere in Asia, and in North America, Europe, and Australia.

5. Where is the best place to plant a rhododendron?

• Rhododendron flowering shrubs prefer cooler climates and grow in a sheltered, semi-shaded spot with gentle morning sun.  However, some varieties in this species such as Vireya rhododendrons are more suited to warm rainforest-like conditions.

Reference:

1. “Azalea.” Encyclopædia Britannica, Encyclopædia Britannica, inc.
2. Loughrey, Sarah Hutchinson, and Janet. “Rhododendron Bushes: Planting, Pruning & Care Info – Garden Design.” GardenDesign.Com, Garden Design Magazine.

Image Courtesy:

1. “Azalea, a member of the genus Rhododendron” By Jim Evans – Own work (CC BY-SA 4.0) via Commons Wikimedia
2. “Rhododendron Forest in the Sagarmatha National Park, Himalaya, Nepal” By GRID-Arendal (CC BY-NC-SA 2.0) via Flickr

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