Last Updated on December 10, 2023
Rhododendrons are beautiful, popular flowering shrubs that can be found in gardens and pots all across the United States. Their blooming periods are quite long and can last from early spring to late fall.
There are many different cultivars of rhododendrons, with brilliant colors that range from pink to fiery reds to white. They enjoy the shade and flourish in both gardens and pots. They are popular flowering bushes that are simple to maintain and provide outstanding fall color.
So how long do rhododendrons bloom? The quick, general answer is this: it takes about three weeks for a rhododendron flower to grow from a bud to a full bloom.
The blooming times of most hardy varieties of rhododendrons is about three months. Some non-hardy varieties can have a slightly longer blooming season, but others only produce flowers for a few weeks each year.
Some rhododendron species have flowering times that take quite a bit longer.
Let’s learn more about the many characteristics of these beautiful flowers!
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What do Rhododendrons Look Like?
Rhododendrons are lush, green plants that grow around 5 feet tall. Their leaves are very large and glossy-looking; quite eye-catching.
They spread through underground stems called rhizomes, which expand to form thick shrubs. Many different species of rhododendron can be found in the United States, most of which are indigenous to Southeast Asia.
There are about 800 different types of rhododendrons, which can be broken down into two categories: hardy and non-hardy.
Most rhododendrons that are hardy generally have a longer blooming season than non-hardy varieties. They spread through rhizomes and can survive in colder climates.
A good example of a hardy rhododendron is the Catawbiense Album, which grows to about 5 feet tall and has big white blooms that start blooming in late spring/early summer.
Non-hardy rhododendrons are generally shorter, have smaller leaves, and have darker colors than their hardy cousins. They grow through suckers and do not spread as easily, which makes them a good choice for planting in pots or in confined areas.
The Variegatum is a popular non-hardy variety that spreads up to 3 feet tall and has pink flowers that bloom from late spring through summer.
Azaleas and Rhododendrons make great garden partners.
Azaleas and Rhododendrons can be planted together in gardens because they require similar environmental conditions. They both like to grow in acidic soil, prefer full or partial shade and do not want to dry out too much during the summer.
So how long do azaleas bloom? While rhododendrons and azaleas are both flowering shrubs, they are different types of plants. Azaleas usually have smaller leaves than rhododendrons and grow to be about 3 feet tall or shorter.
They also prefer more acidic soil than rhododendrons. They spread through suckers rather than rhizomes, which makes them less ideal for planting in gardens and more ideal for planting in pots.
Azaleas bloom earlier than rhododendrons, usually between late winter and mid-spring. Their flowers range from white to pink to red, depending on the type of azalea that is planted.
When do Rhododendrons Bloom?
In general, R. Catawbiense blooms from early spring into summer.
Rhododendrons that are hardy in zones 5-9 generally begin to bloom when nighttime temperatures drop below freezing and days are clear and sunny. They stop flowering when the weather gets too hot or too cold.
Non-hardy rhododendrons also need cool nights in order to produce blooms. Hardy varieties are more tolerant of cold weather, though both varieties perform best when temperatures do not exceed 90 degrees F.
Rhododendron plants that are grown in containers have a slightly different blooming schedule than those planted in gardens. For container-grown rhododendrons, it will take a little longer for the flowers to appear.
How Long do Rhododendrons Bloom?
Rhododendrons have a fairly long blooming season with various blooming times. Depending on the cultivar, their flowering time is from late winter/early spring through summer and early autumn.
In mild and maritime climates, you’ll find that both rhododendrons and azaleas may continue blooming for up to seven months.
The Catawbiense Album will produce flowers for about 3 weeks, from mid-spring to early summer.
The Variegatum will have flowers that last from late spring through early autumn.
Most hardy varieties will produce flowers for around 3 months. Some non-hardy varieties can have a slightly longer blooming season, but others only produce flowers for a few weeks each year.
Many rhododendrons have a reputation for being slow-growing, but that is usually an unfounded myth. They grow quickly when young, and will only take a few years to reach mature size if cared for properly.
Rhododendrons need regular watering to remain healthy and produce flowers, though they do not require much fertilizer or pesticides. It is best to fertilize once in early spring and once before autumn, which can help promote continuous growth and enhance the flowers’ blooms.
Make sure that your rhododendrons are planted in an area with plenty of shade; they will produce their best flowers in the shade!
If you want to ensure that your rhododendrons continue to produce flowers for as long as possible, remove the wilted rhododendron bloom, also called deadheading.
You should also prune your rhododendron plants at least once each year. A lot of people think that you should wait until after flowering is finished in autumn, but it should be pruned in early spring while it is still dormant.
How Long Do Rhododendron Blooms Last?
As stated above, the rhododendron flowering period lasts around 3 weeks. A bud emerges on one of the upper branches about 10 days before it opens to form a flower head.
This process generally takes place over three stages that can last anywhere from 1-2 days to 3 weeks. Once it is fully opened, rhododendron blooms will usually last a full week before wilting and dying.
Rhododendrons enjoy the shade, and do best in moist soil that is acidic or neutral. Some cultivars need more sun than others, but most species will want filtered sunlight to half-sun. Their soil should be kept moist but not soggy, and fertilization is essential for good blooming.
How to Make Rhododendrons Last Longer
Although the rhododendron flowers have a lengthy blooming period, unlike many others, you may want to extend it so that you can enjoy them for longer. There are several ways you can do that very easily. If your rhododendrons bloom early, you can keep them safe from frost, allowing their bloom to last longer.
Once a rhododendron has finished blooming, it is important to remove, or deadhead, the flowers to promote new growth and reduce disease risk.
If your rhododendron is in a pot, cut the stems just above the surface of the soil. When planting rhododendrons in the ground, cut them back from about 12 to 20 inches inches above the ground, staggering the heights throughout the bush.
Rhododendrons are susceptible to disease if their soil is too moist or stays wet for extended periods of time. They cannot survive frost, so it is important not to expose them to temperatures below 30ºF.
How to Know Which Species of Rhododendrons will Grow in Your Garden
Rhododendrons can vary in size, shape, color, and scent. They are available in a wide range of hybrid varieties that each grow well under different conditions. Some flowers are fragrant to help attract pollinators, while others may have various leaves or bark colors. The selection is large enough that you should be able to find one that is well-suited for your garden.
As discussed, there are many different types of rhododendrons available for purchase, but it can be difficult to determine which one is right for your garden conditions.
It’s always best to check with your local garden shops or nursery and talk with an expert who can give you direction.
Conclusion: How Long do Rhododendrons Bloom?
Rhododendrons are beautiful flowering plants that produce blooms for about 3 weeks. For the best blooms, make sure to prune your rhododendron after it has finished blooming and cut out any dying material.
The Catawbiense Album will have flowers for around 3 weeks, while most hardy varieties will produce blooms for around 3 months.
After the flowers have wilted, prune your rhododendron to keep it healthy and help promote future blooming.
Thanks for reading, and I hope you learned more about the beautiful rhododendron!