Rhododendrons, Azaleas... is there much of a difference? Well, yes! Let our horticulturalists take you through everything you need to know about Azalea flowers and Rhododendron flowers, from how they bloom to their foliage and maintenance requirements.
Difference between Azalea and Rhododendron flowers
Both Azalea flowers and Rhododendron flowers are beautiful (and similar) to behold. Although these ornamental flowering shrubs were once separate, they are now both categorised under the genus Rhododendron.
Horticulturalists, especially those of the American Rhododendron Society, are painfully aware of the difference between the Azalea and Rhododendron varieties. At Gardeners Dream, we carefully label all our plants to make differentiating simple, too. However, many gardeners still use the terms interchangeably, which leads to quite a bit of confusion!
Both have notable differences that are important to know when choosing which to grow... especially considering the difference in size when fully established. So, here's how the Azalea vs Rhododendron battle pans out.
Leaves
Rhododendrons - large, thick leaves. Rhododendrons tend to have larger leaves with a leathery thickness. Some have small spots or scales on the leaf undersides, but not all Rhododendrons have this.
Azaleas - small, thin leaves. Most azalea species have smaller pointed leaves with smooth-surfaced undersides.
Leaves are a good first indicator of the botanical differences between Azaleas and Rhododendrons.
Size
Azaleas - small and bushy. Most azaleas stay small and manageable, with some beautiful Azaleas reaching full height at just two feet tall.
Rhododendrons - larger shrubs. Most rhododendrons get quite large, with some growing into small trees. The largest varieties in the genus Rhododendron can reach 20 feet.
Hybrids and cultivars are often bred to limit heights - keep this in mind when searching for a shrub for your home landscape.
Blooms
Azaleas - solitary flowers. One to three azalea flowers per stem.
Rhododendrons - flower clusters called trusses. Almost all Rhododendron flowers grow in dense clusters.
Both Azaleas and Rhododendrons have a bloom time that can stretch from early spring through to autumn, with most having a lush display in early summer at the least. This can vary depending on the exact variety and the current climate.
Flowers
Azaleas - produces funnel-shaped flowers with up to five stamens per flower. Stems are slender and many.
Rhododendrons - known for bell-shaped flowers or trumpet-shaped flowers. Each flower has 10 or more stamens. Stems are short and few.
Another similarity between Azaleas and Rhododendrons is the flower colours. Purple, orange, yellow, white, red and pink are all common, though Azaleas tend to have more varied shades. You might find that Azaleas have stronger fragrances, too.
Growth habit
Azaleas - though you may find some evergreen Azaleas in warm climates (or as indoor plants), the deciduous Azalea is most common in the UK garden.
Rhododendrons - most Rhododendrons are evergreen, though you may find a few deciduous species that drop leaves in the autumn.
| Azalea | Rhododendron | |
| Number of Stamens | Usually 5 but up to 10 | 10 or more |
| Flowers | Usually Solitary/Terminal | Almost Always in Trusses |
| Leaves - Texture | Soft and Smooth | Leathery or Scaly Underneath |
| Leaves - Size | Smaller and Thinner | Bigger and Thicker |
| Flower Shape | Tube-Funnel-Shaped | Bell-Like |
Though they are closely related, you'll find mostly deciduous Azaleas and evergreen Rhododendrons. However, as there are many hybrids across the Rhododendron genus, it can be hard to determine growth habits without consulting a horticulturist or checking the variety details.
Should you grow Azalea or Rhododendron?
When you're trying to settle the Azalea vs Rhododendron debate, there is more to consider than just aesthetics. Both Azaleas and Rhododendrons have gorgeous flowers anyway! You also need to think about upkeep for deciduous vs evergreen shrubs and preferred growing conditions.
P.S. If you can't decide between Azaleas and Rhododendrons, plenty of other garden shrubs rival these two plants.
Planting
Azaleas - shallow rooted plants that need well-draining soil. Good for flower beds and containers.
Rhododendrons - large woodland shrubs that need space. Don't plant too close to other trees or structures.
Both Rhododendrons and Azaleas thrive in well-draining soil, and they also prefer slightly acidic soil. Plant them in autumn or early spring so they can establish before the flower buds grow. Even though Rhododendrons grow large, they also have shallow roots - you don't need to dig a deep hole.
Care
Azaleas - two to three inches of mulch will make growing Azaleas successful. Leaves or composted bark is the preferred organic matter. Use rainwater to keep the soil moist.
Rhododendrons - mulch with a few inches of organic matter - leaves or bark. Use rainwater to keep the soil moist.
For both Azaleas and Rhododendrons, replenish the mulch yearly in the spring. Both plants also like plenty of water; however, you should avoid using tap water throughout the garden house. The calcium in your water supply can reduce soil acidity, so stick to rainwater instead.
So long as the soil remains acidic and you mulch yearly, neither plant will require feeding. Mulching should also prevent the soil from drying out or becoming waterlogged, which can lead to leaf drop.
Pruning
Azaleas - deciduous Azalea varieties respond well to a hard cutback. You can also deadhead flowers. Otherwise, cut back dead wood as needed.
Rhododendrons - pruning is only necessary if you need to maintain the size or to remove dead branches. Like most shrubs, pruning is best done after the flowers have faded. If you need to do a heavy cutback, wait until winter.
While you prune Azaleas and Rhododendrons, keep an eye out for pests. Indoor Azaleas can be prone to spider mites. Outdoor varieties may be susceptible to leaf scorch during frosts.
Sun exposure
Azaleas - partial shade and darker corners of your garden suit many deciduous varieties. In the UK, our cooler climate also means Azaleas can handle full sun positions. Getting the right amount of filtered sunlight will encourage more blooms.
Rhododendrons - dappled shade is usually best, though some alpine evergreen Rhododendrons prefer full sun. Avoid deep shade beneath trees or beside structures.
Most Azaleas and Rhododendrons thrive in partial shade or full sun conditions; the main consideration when choosing a spot is the size of the plant once fully grown.
With the main differences highlighted in our Azalea vs Rhododendron comparison, it's now time to make a choice. You can find both varieties, as well as many other flowering shrubs suitable for the UK climate, at Gardeners Dream. Did you know that we offer free delivery over £50 when you shop our garden shrubs?
Quickfire FAQs
When do Rhododendrons bloom?
Rhododendrons bloom in the spring or summer.
When do Azaleas bloom?
Azaleas bloom in the spring, summer or autumn.
Are Azaleas evergreen?
Most Azaleas are deciduous, though evergreen Azaleas do exist and make great houseplants.
Are Rhododendrons evergreen?
Yes, most Rhododendrons are evergreen shrubs, though deciduous Rhododendrons do exist.
