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Rhododendron and azalea species are found growing in the wild from the arctic region to the tropics. Regions suitable for growing rhododendrons and azaleas are those that have naturally acidic soils, adequate water availability, moderate humidity and winds and lack of temperature extremes. In the U.S. such regions run along the east and west coasts, along the Gulf of Mexico and around the Great Lakes.
The climate of the U.S. Pacific Northwest region, especially between the Cascade Mountain range and the Pacific Ocean, is very accommodating to the growth of many types of rhododendron hybrids and species. The favorable climate extends down the coast to the San Francisco Bay area, which is about the southern limit for growing the large-leaved elepidote Large leafed, large-sized plants at maturity, that do not have scales on the underside of the leaves.varieties. Many varieties of small-leaf lepidote Small leafed, usually low growing plants, often bloom earlier than elepidotes, with small scales on the leaf undersides.rhododendrons also thrive in gardens along the U.S. west coast states.
With attention to suitable hardiness, large-leaf rhododendron varieties do well in the eastern United States, generally along the Atlantic coast from Nova Scotia to the upper Carolinas, along both sides of the Appalachian Mountains and in southern Ontario, Michigan, Illinois, Wisconsin, Ohio, Pennsylvania, New York, New Jersey and Connecticut.
Evergreen and deciduous azaleas do well on the west coast from British Columbia to the Mexican border, along the Gulf Coast and throughout the southeastern U.S. and along the east coast up into the Boston area. Some deciduous azaleas are very cold hardy and some tolerate heat and humidity. At least two species of deciduous azaleas are native to eastern Canada and several more species are found in New England. Many species of deciduous azaleas are native to the east, southeast and south and one species grows wild in the west. Hybrids derived from the native species thrive over large areas of the United States.
Throughout most of the Middle West and the Great Plains rhododendrons can be grown with special attention to growing conditions, and selecting very hardy varieties. When placing plants choose locations that mitigate extreme temperature changes, especially in spring and fall, and provide protection from drying summer or winter winds.
Some of the maddenii-type rhododendrons grow quite readily in southern California. The tropical vireya rhododendrons do well in the Los Angeles basin, and can be grown outdoors in Florida, Hawaii and in parts of Australia and New Zealand.
For many decades rhododendron and azalea hybridizers have been busy creating new cultivars that have extended the range of flower color, bloom time, plant size, and hardiness, resistance to disease, etc. This has greatly expanded the regions where rhododendrons and azaleas can be successfully grown.
More information about rhododendron and azalea suitability in the landscape can be found in the following Journal ARS articles:
Growing Azaleas In New England by Charles W. Findlay, Jr.
Summer-blooming Weston Hybrids by C. J. Patterson
Growing Rhododendrons and Azaleas in the Middle Atlantic States by Sandra McDonald
Rhododendrons in Middle America by Donald W. Paden
Reliable Rhododendron Species for Pacific Northwest Woodland Gardens by Rudolph Henny
Growing Rhododendrons in Warm Climates by Willis Harden
Evergreen Azaleas Up From Inferiority by Franklin H. West
Index of Contents
Pruning & Spent
Propagation & Hybridizing
Insect & Disease Control
- Rhododendron Shrub
- Colorful Combinations
- Rhododendron Care Must-Knows
- Rhododendron or Azalea?
- More Varieties for Rhododendron
- Autumn Chiffon Encore azalea
- Bloom-A-Thon® series rhododendron
- Blue Diamond rhododendron
- Bollywood® rhododendron
- Capistrano rhododendron
- Cecile azalea
- Hydon Dawn rhododendron
- Hiryu azalea
- ‘Fielder’s White’ azalea
- Gibraltar hybrid azalea
- Karen azalea
- ‘Mandarin Lights’ rhododendron
- ‘Purple Dragon’ azalea
- Hino Crimson azalea
- Korean azalea
- Nova Zembla rhododendron
- ‘Nuccio’s Carnival’ azalea
- Olga Mezitt rhododendron
- Rosy Lights azalea
- ‘Rose Queen’ azalea
- Sun Chariot rhododendron
- Trude Webster rhododendron
- ‘White Grandeur’ azalea
- Garden Plans For Rhododendron
- Rhododendron species
- Flowering Season
- Peter Cundall: Happy to be left in the shade
- Shade – The “Good” Stuff
- Zone 5 Rhododendrons – Tips On Planting Rhododendrons In Zone 5
- How to Grow Rhododendrons for Zone 5
- Hardy Rhododendron Varieties
- Northern Lights Azaleas
- Easiest to Grow – Rhododendron catawbiense
- Best Compact Rhododendron – ‘PJM’ Rhododendron
- Best Cold Weather Plant – Northern Lights Azaleas
- The Best Re-Blooming Bushes – Encore Azaleas
- Showiest Blooms – Amelia Rose Azalea
- Most Fragrant – Rhododendron colemanii
- Best Variegated Foliage – Bollywood Azalea
- Do you have any favorite Azalea or Rhododendron varieties? Tell us in the comments below.
This family of plants contains an option for every landscape, from the giant rhododendrons of East Asian mountainsides to the rosebay rhododendrons native to Eastern U.S. woodlands. These often-broadleaf evergreen plants boast large clusters of showy blooms at their growing tips in spring. In areas where dry winters tend to desiccate evergreen types, deciduous varieties of rhododendrons can fill in the gap.
A classic shade garden plant, rhododendrons are prized for their glossy green foliage and showy clusters of blooms. Coming in a wide variety of colors, the most common flowers are borne in ranges of purples and pinks into whites. Many of the deciduous types also boast bright yellow and orange hues that work wonders in brightening up shady corners of the garden.
Rhododendron Care Must-Knows
The rhododendron is a wonderful addition to any shade garden. Deciduous varieties can hold up much better to more sun, as many of the evergreen types can be susceptible to burn in winter where they are exposed. To prevent this, plant evergreen types in sheltered areas, avoiding southern exposures since warm and sunny winter days can be fatal. Keep them sheltered from drying winter winds as well. Evergreen types may begin to curl their leaves during the winter, and this is actually a physiological response to dry winter weather. By curling their leaves, they are protecting themselves from cold temperatures and winds in order to prevent potential winter burn.
Why your rhododendron’s leaves are curling.
Rhododendron plants, much like many other plants in the Ericaceae family, prefer acidic soils. Ideal soil pH for rhododendron plants is somewhere between 4.5 and 6.0. If you have had problems growing rhododendrons in the past, perform a soil test. You can amend the soils with peat moss, compost, and other soil acidifiers to keep them happy.
Rhododendron also appreciates organically rich soil. This will keep the shrubs decently moist and prevent them from drying out—dry winters and late falls can be particularly fatal to rhododendrons. On the other end of the spectrum, overly wet soils can also be fatal to rhododendrons. Finding the right balance of moisture in soils can be tricky.
Pruning may be necessary to create a more desirable shape and overall more visually appealing plant. After the plants have bloomed, spent blossoms can be cut back to the new growing tips. After bloom is also the ideal time to do any other pruning. Damaged or diseased growth should always be removed to prevent the spread of disease. You can also do rejuvenation pruning by cutting older plants back more severely to encourage better branching.
More Evergreen Shrub Varieties
Rhododendron or Azalea?
Rhododenrons and azaleas often get confused. A while back, azaleas were considered a separate genus of plants, but since they have been found very genetically similar to rhododendrons, today they are lumped in the same genus. Now, azalea has become more of a common name within certain types of rhododendrons. People tend to think of rhododendrons as larger evergreen plants with big clusters of blooms. “Azaleas” are what people tend to associate with deciduous rhododendrons, and generally have smaller leaves and shorter plant habits.
More Varieties for Rhododendron
Autumn Chiffon Encore azalea
Rhododendron ‘Robled’ offers light pink flowers in spring, summer, and fall. It grows 3 feet tall and wide. Zones 7-9
Bloom-A-Thon® series rhododendron
A series of semi-evergreen azaleas that feature a re-blooming habit for season long color. Zones 6-9
Blue Diamond rhododendron
Rhododendron ‘Blue Diamond’ is a dwarf evergreen rhododendron that bears violet-blue flowers. It grows 5 feet tall and wide. Zones 7-9
Beautiful cream variegated foliage sets this variety apart, with bright magenta flowers in the spring on dwarf plants that make great container plants. 2-3 feet tall and wide. Zones 6-9.
Rhododendron ‘Capistrano’ is a compact, mounding selection, growing to 4 feet tall and wide, bearing trusses of frilled greenish-yellow flowers. Zones 6-8
Rhododendron ‘Cecile’ grows vigorously to become a dense, 7-foot-tall and 7-foot-wide shrub with trusses of large, salmon-pink flowers. Zones 5-8
Hydon Dawn rhododendron
Rhododendron ‘Hydon Dawn’ is one of the few rhododendrons that tolerates full sun. It has a low, compact habit to 5 feet tall and wide and bears clusters of small, clear pink flowers that fade to white. Zones 7-9
Rhododendron obtusum amoenum is a dense, low-growing evergreen azalea that bears reddish-violet to crimson flowers. It grows 18 inches tall and 3 feet wide. Zones 6-9
‘Fielder’s White’ azalea
Rhododendron ‘Fielder’s White’ is blanketed with single white blossoms in mid-spring. Evergreen foliage complements the 3-inch-wide flowers on this variety. Zones 8-9
Gibraltar hybrid azalea
Rhododendron ‘Gibraltar’ grows vigorously to 5 feet tall and wide, bearing bright orange flowers. Can tolerate full sun. Zones 5-8
Rhododendron ‘Karen’ is a hardy evergreen azalea bearing purple flowers in spring. It grows 3 feet tall and wide. Zones 4-9
‘Mandarin Lights’ rhododendron
A deciduous type azalea, it features bright orange blooms in spring on naked stems before the foliage emerges. 4-5 feet tall. Zones 3-7
‘Purple Dragon’ azalea
Rhododendron ‘Purple Dragon’ features striking dark purple-red flowers that open at the branch tips in late spring. The shrub grows 3-4 feet tall and wide. Zones 7-9
Hino Crimson azalea
Rhododendron ‘Hino Crimson’ is a dwarf, densely growing azalea that produces bright red flowers. It grows 2 feet tall and wide. Zones 5-8
Rhododendron yedoense poukhanense bears lilac to deep-rose funnel-shaped flowers in spring. In fall, leaves change to a gold or reddish purple. Grows 6 feet tall and wide. Zones 5-9
Nova Zembla rhododendron
Rhododendron ‘Nova Zembla’ is a large evergreen shrub that bears trusses of deep red flowers with spotted throats. It grows 5 to 10 feet tall and wide. Zones 5-8
‘Nuccio’s Carnival’ azalea
Rhododendron ‘Nuccio’s Carnival’ presents a profusion of large, single to semidouble magenta blossoms that add a burst of color to the landscape. Flowers are backed by rich green evergreen foliage. Zones 8-9
Olga Mezitt rhododendron
Rhododendron ‘Olga Mezitt’ is an evergreen selection that produces small trusses of deep peach-pink flowers. The leaves redden in fall. It grows to 4 feet tall and wide. Zones 4-8
Rosy Lights azalea
Rhododendron ‘Rosy Lights’ is a deciduous azalea that offers extra cold hardiness. The shrub grows to 4 feet tall and wide and features deep purple-pink flowers. Zones 3-8
‘Rose Queen’ azalea
Sun Chariot rhododendron
Rhododendron ‘Sun Chariot’ is an upright, dense-growing spring-blooming variety that grows 6 feet tall and wide. It bears yellow blooms with orange blotches in large clusters. Zones 6-9
Trude Webster rhododendron
Rhododendron ‘Trude Webster’ forms a compact, upright plant with clustered, clear pink flowers. It grows 5 feet tall and wide. Zones 6-9
‘White Grandeur’ azalea
Rhododendron ‘White Grandeur’ has long-lasting white flowers dotted with green speckles in mid-spring. This small evergreen cultivar grows 2-3 feet tall and wide.
Garden Plans For Rhododendron
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This large genus in the heath (Ericaceae) family includes some 800 species, which are widely distributed across the Northern Hemisphere, with the majority growing in temperate to cool regions. Gardeners can choose from many different types of rhododendrons: alpine rhododendrons, with small leaves, wiry stems, and clusters of tiny flowers; shrub rhododendrons, including those up to 4.5m tall; tree rhododendrons, with a single trunk and a large head of foliage; evergreen azaleas, which are low to tall bushes with semi-persistent foliage and large light-textured flowers; deciduous azaleas, which are large twiggy bushes with flowers usually in shades of yellow, red, or orange; and vireya rhododendrons, which are tender tropical species with funnel-shaped blooms and no fixed flowering season.
Rhododendron foliage is extremely variable. Most species bear “trusses” of up to 24 spectacular blooms, in colours ranging from white to pink, red, yellow, and mauve. Flowers are often multi-coloured, with spots, stripes, edging, or a single blotch of a different colour in the throat of the flower. With the exception of some vireya species and hybrids, fragrant rhododendrons are always white or very pale pink. Blooms vary in size and shape but are generally bell-shaped, appearing from early spring to early summer. The fruit is a many-seeded capsule, normally woody, with the tiny seeds sometimes bearing wings or tail-like appendages to aid dispersal.
In common with most heath family plants, rhododendrons prefer acidic soils, high in organic matter and freely draining, in a partly shaded position. While most prefer some protection from wind, sun, and frost, many others tolerate these conditions. Species may be raised from seed, or propagate from half-hardened cuttings or layers.
Gardening Australia suggests you check with your local authorities regarding the weed potential of any plants for your particular area.
© Global Book Publishing (Australia) Pty Ltd from Flora’s Gardening Cards
Peter Cundall: Happy to be left in the shade
I NEVER fail to be astonished by the huge number of ornamental plants that appear to grow quite contentedly in fairly deep shade.
These are places close to south-facing walls of large buildings and most homes — places that rarely see sunlight.
The only snag with many shade-tolerant plants is that, although growing with healthy vigour, despite low light, they rarely flower, so we have to be content with the foliage.
Even so, there are still many easily obtained shrubs and small trees with highly attractive, even colourful leaves that are worth searching for.
For example the eternally-popular Japanese Laurel (Aucuba japonica) loves the shade and fails to thrive in full sunlight.
The variety Gold Dust is a real beauty, a dense evergreen, growing about 1.5m tall and wide.
The large shining, deep-green leaves are covered with golden splashes, some just clusters of tiny specks. The sparkling glow produced brightens up gloomy corners of any garden.
The original form, without leaf speckles, produce vibrantly green, glistening, overlapping leaves
At the end of each growing season this Japanese laurel gives us a special reward.
Great bunches of gleaming, bright red, pea-size berries hang in glorious clusters, half hidden by the leaves.
Many rhododendrons are also at home in deep shade, especially those with large leaves.
For most, lack of light means they produce only growth buds and shoots, but the handsome leaves often make up for lack for flowers.
The remarkable exception is R. macabeanum, mostly grown for its enormous, beautifully marked foliage.
It’s these huge leaves that enable this shade-loving plant to harvest and fully use every tiny pin-point of light they can capture.
Better still, this ability to collect light is not only enough to stimulate strong growth, but enables the production of great trusses of creamy-yellow flowers.
To see Rhododendron macabeanum in full bloom in some impossibly shady corner is a revelation.
It’s just another illustration of the remarkable determination of some plants to grow, flower, set seed and reproduce, despite difficult and even hostile environments.
And of course this being a species of rhododendron means that after germination, these tiny seeds always come true.
Other plants that are able to grow and flower in fairly deep shade include several varieties of St John’s Wort (Hypericum).
There are numerous species and cultivars of hypericum, most of which remain pest and disease-free.
This is due to certain substances in the leaves and stems.
Among the most effective for heavy shade is the strong-growing groundcover (H. calycinum) usually found under common names such as Aaron’s Beard or Rose of Sharon.
This rather lovely — but sometimes invasive — plant produces countless clear-yellow, cup-shaped flowers, each about 40mm in diameter. It requires little feeding, but an occasional deep watering during dry periods.
It spreads by underground stolons and can cover several metres of bare, shady ground in a few months.
Should Aaron’s Beard begin to spread too widely, all the invading parts are easily pulled from the ground.
A point worth noting is that St John’s Wort (pronounced “wert”) is also a popular medicinal herb, but one that must be used with great care.
This is one herbal remedy that must never be taken if other forms of medication are also being used.
Rowallane is probably one outstanding hypericum hybrid — a two-metre shrub that displays the most flamboyant yellow flowers.
I planted ours in medium shade 25 years ago and despite being pruned back hard each May as flowering ceases, it’s still going strong.
Worth a mention is Clivia miniata, a kind of semi-bulbous member of the Amaryllis tribe.
This leafy plant produces yellow to pale red flowers in places where other plants cannot do so because of low light.
Any well-drained position with slightly acidic soil is ideal and the only problem is we have to wait several years after planting before they begin to bloom.
All clivia species can be grown successfully in large pots and after about 10 years many become seriously root-bound.
It’s a simple matter to transfer them to slightly larger containers, a job best carried out when the first frustrated, searching roots begin to emerge from drainage holes.
Shade – The “Good” Stuff
This article completes our series on shade gardening, at least for now. We have covered the basics of shade gardening, strategies for dealing with the worst shade conditions and plants and strategies for mediocre shade. This time we are covering “good” shade conditions and the wide array of plant that will thrive in shade. The earlier articles covered some of the shade plants that can tolerate tougher shade conditions, you can learn about plants for more difficult shade conditions by referencing the articles above.
The great news about “good” shade is that this kind of shade gardening is just as easy as sun gardening. We previously defined “good” shade as areas that get morning and/or late afternoon sun, receive dappled shade all day and areas that are bright, but not sunny. Tree roots or dark spots don’t complicate this type of shade; this means that you have all of the various shade plants to play with. To quote my favorite baseball announcer, Jack Buck, “Go crazy folks! Go crazy!” I unfortunately do not get to play with “good” shade in my garden. I have wonderful light, but deep tree roots do limit my plant selection. My mom, on the other hand, can tap into any shade plant out there. She also has gorgeous light from shade trees, but the raised beds are around her porch rather than actually under the trees – perfect conditions for shade plants.
Some of the plants that will take less ideal shade conditions are English Ivy Hedera, Liriope, Ajuga, Ferns, Brunnera, Lily-of-the-Valley(Convallaria), Hosta, Heuchera, Helleborus, Astilbe, Dicentra, and Impatiens. All of the plants that will do well in tougher shade conditions, will thrive in the best shade conditions.
The most common shade annual categories are probably Impatiens, Torenia, Begonia, Coleus and Fuchsia. I have covered all of these, except Fuchsia previously. Fuchsia is a great shade plant. Many of us may think of them mainly for use in containers, but they can be planted in the landscape as well. Fuchsias come in a range of colors. The flowers are single to double. In addition to the standard Fuchsia, there are several other species available that are larger more landscape types of plants. If you live in an area with mild winters (zones 7-9), Hardy Fuchsia (Fuchsia genii) are a good perennial landscape option for shade.
Perennials are where you can really start to have a lot of fun with “good” shade conditions. Here are some plants to consider:
Aruncus, Goat’s Beard, has fern-like foliage and will bloom from early to mid-summer with feathery, spikes of white blossoms. Yellow to orange foliage gives it a second season of color for the garden.
Cimicifuga, is a native plant that is hardy in zones 4-8. It likes consistently moist soil and can take several years to establish well in the garden. However, it is worth the time. Look for black foliaged varieties. It is a larger plant, up to 4 feet and blooms late in the season.
Lamium, (photo left) Spotted Dead-Nettle, generally has green and silver variegated foliage and pink or white flowers. However, it does come with gold and green foliage as well. It is hardy to zone 3.
Ligularia, is very cold tolerant. It is usually hardy to zone 4, with some versions hardy to zone 3 and others only hardy to zone 6. Be sure to check the plant tag before buying to be certain of the specific hardiness. This is another plant that must have moist soils, do not allow soil to dry. Often one of the larger plants available for shade gardens, up to 5 feet, more compact forms that are appropriate for smaller gardens are also available. The large, serrated leaves are interesting even before the spikes of yellow flowers appear in mid-summer.
Polygonatum ‘Variegatum’, Variegated Soloman’s Seal, is a classic shade plant. Grown mostly for it’s variegated foliage it does have pendulous white blooms. It is hardy to zones 3.
Tricyrtis, Toad-Lily, is one of the few members of the Lily family to prefer shade. They tend to be late to emerge in spring, so don’t worry if you don’t see them when the rest of your perennials start to appear. Have patience, they like to take their time. Their biggest attraction is their orchid-like flowers. Because the flowers are so unique, you might want to place the plants near seating areas or along pathways where they can be admired up-close. They do prefer consistently moist conditions. They are generally hardy to zone 5, but can be as hardy as zone 4 or only hardy to zone 6, check the plant tag or online sources for variety specific information.
It is often easy to think of plants for your garden bed as being restricted to annuals and perennials, but that would be a huge disservice to the shrubs that can add another dimension to both shade and sun plantings. Incorporating shrubs into your planting beds is one of the best ways to integrate shrubs more seemlessly into your garden. In a previous article we mentioned Dream Catcher™ Kolkwitzia, Hibiscus syriacus and Celtic Pride™ Microbiota. Here are some additional shrubs that will work in “good” shade conditions.
Abelia, (photo right) will do well in part shade gardens, but not full shade. They are generally hardy to zone 6, but some may survive in zone 5. Newer cultivars, such as those in our collection, are compact enough to work in smaller gardens and usually feature several seasons of color including spring flowers and fall foliage color. Abelia is also not a favorite of deer
Amelanchier, Serviceberry, is a group of shrubs and small trees that are native to many parts of the U.S. and Canada. They bloom in early spring and then form fruits that are a good food source for wildlife. Fall color adds to their appeal. They are generally hardy to zone 4.
Itea, is a useful native plant with lots of potential for the home landscape. It prefers moist soils and will tolerate wet conditions. It will grow in full sun to full shade, and requires little pruning or other maintenance. The variety Little Henry® has lightly scented, pure white flowers that shoot like fireworks in early summer. Its mounded, compact stature makes it an improvement over older varieties. Maturing at less than 3 feet tall, it is suitable for flooding large banks with mass plantings. It is also a delightful addition to the mixed border. Then when you’re not expecting anything more from this little wonder, its green summer foliage changes to a brilliant multitude of oranges and reds in the fall, making Little Henry® a rewarding experience through out all seasons. It is hardy in zones 5-9.
Rhododendrons and Azaleas can be confusing, but one thing we know for sure is they are one of the showiest classes of shrubs for shade conditions. You, like me (before I dug into the research for this article), might be confused as to what the difference is between an Azalea and a Rhododendron. Well, in the words of the New York Chapter of the American Rhododendron Society, “all Azaleas are Rhododendrons, but not all Rhododendrons are azaleas.” At one time, Azalea and Rhododendron were two separate genera, but they are now all considered to be Rhododendrons. The best rule of thumb is that Azaleas are mostly deciduous, while Rhododendrons are usually evergreen. This rule of thumb won’t always be right, but it will be right much more often than it is wrong. However, the most important thing, whether we are talking about an Azalea or a Rhododendron, is that both types of plants are very showy shade garden plants.
The hardiness for Rhododendrons will vary considerably. Some will be hardy to zone 3, while others are only hardy to zone 7. Make sure you are selecting a plant that is hardy for your conditions. Plant breeders have put forth a lot of effort to select more hardy plants for this genus and we get to benefit from their decades of effort. This article, from University of Minnesota Cooperative Extension, is a good rundown of the hardiest Rhododendrons including Azaleas.
One of the newer developments in Azalea is plants that will not only put on a show in spring, but will rebloom. The Bloom-A-Thon® series, like other azaleas, will bloom in spring and this flowering period will last several weeks. Once the spring flowers fade, the plant takes a brief rest and by early July, is gearing back up for its summer flowering. The breeder says that it is actually this July-August period that is their true shining moment, and that the display is even more spectacular than the spring one. After the summer bloom, the plant doesn’t take the same rest again, but continues to put out flowers until mid-November, when cold weather has really set in and the days are considerably shorter. They are hardy in zones 6-9 and come in 4 colors.
There are certainly other shade plants available, but this should give you a good starting point.
Little Henry® Itea virginica’Sprich’ PP: 10988; Gaelic® Spring Pulmonaria ‘Irish Spring’ PP: 14015
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Zone 5 Rhododendrons – Tips On Planting Rhododendrons In Zone 5
Rhododendron shrubs provide your garden with bright spring flowers as long as you site the shrubs in an appropriate location in an appropriate hardiness zone. Those who live in cooler regions need to select hardy rhododendron varieties to be sure the bushes make it through the winter. For tips on planting rhododendrons in zone 5, as well as a list of good zone 5 rhododendrons, read on.
How to Grow Rhododendrons for Zone 5
When you are planting rhododendrons in zone 5, you need to recognize that rhododendrons have very specific growing requirements. If you want your shrubs to thrive, you need to take their sun and soil preferences into account.
Rhododendrons are called the queens of the shade garden for good reason. They are flowering shrubs that require a shady location to grow happily. When you are planting rhododendrons in zone 5, partial shade is fine, and full shade is also possible.
Zone 5 rhododendrons are also particular about soil. They need moist, well-drained, acidic soils. Hardy rhododendron
varieties prefer soil fairly high in organic matter and porous media. It’s wise to mix in topsoil, peat moss, compost or sand before planting.
Hardy Rhododendron Varieties
If you live in a region classified as zone 5, your winter temperatures can dip well below zero. That means that you’ll need to select rhododendrons for zone 5 that can survive. Fortunately, the Rhododendron genus is very large, with 800 to 1000 different species – including the entire azalea clan. You’ll find quite a few hardy rhododendron varieties that will do well as rhododendrons for zone 5.
In fact, most rhododendrons thrive in USDA hardiness zones 4 to 8. If you are pining for azaleas, you’ll have to be a little more selective. Some thrive down to zone 3, but many don’t grow well in such cold regions. Avoid species that are borderline hardy in favor of plants hardy to zone 4 if possible.
You find some top choices for zone 5 rhododendrons in the Northern Lights Series of hybrid azaleas. These plants were developed and released by the University of Minnesota Landscape Arboretum. Northern Lights rhododendrons are not just borderline zone 5 rhododendrons. They are hardy in regions where temperatures drop to -30 degrees to -45 degrees Fahrenheit (C.).
Take blossom color into account when you are picking zone 5 rhododendrons from the Northern Lights series. If you want pink flowers, consider “Pink Lights” for pale pink or “Rosy Lights” for deeper pink.
Rhododendron “White Lights” produce pink buds that open to white flowers. For unusual salmon colored flowers, try “Spicy Lights,” a shrub that grows to six feet tall with an eight-foot spread. “Orchid Lights” are zone 5 rhododendrons that grow to three feet tall with ivory colored flowers.
While Northern Lights are reliable as zone 5 rhododendrons, your selection is not limited to this series. A variety of other zone 5 rhododendrons are available.
Northern Lights Azaleas
(Editor’s Note: This article was originally published on January 9, 2008.)
The genus Rhododendron is perhaps the most important genus of flowering shrub grown by gardeners in temperate regions of the world. Certainly, there are literally thousands of hybrids and more being developed every year! Of course, the problem with this genus is that most are not particularly hardy, especially the evergreen types. Deciduous azaleas are slightly hardier since they don’t have winter foliage. However, the standard azalea hybrids; the Exbury, Knap Hill and Ghents, are still only reliably hardy to USDA zone 5.
Recently, there has been significant breeding to develop hardier azaleas and rhododendrons. A whole series of super hardy evergreen rhododendrons are being developed in Finland, while closer to home, there is a series of very hardy deciduous azaleas called the ‘Northern Lights’ azaleas. These hybrids were developed at the University of Minnesota. Hybridizing started in 1957 but the first release was not until 1978. Breeding is still being carried out with two new releases in 2005. Most of the Northern Lights azaleas are hardy to -30 F or -34 C, allowing them to be successfully grown in USDA zone 4, with some even being successful in USDA zone 3. Many of these hybrids were the result of crossing the very hardy American species, R. prinophyllum and R. canadense to various Exbury-type Azaleas. While many of the resulting hybrids have smaller flowers than the standard azaleas, several do have reasonably large trusses. Many are fragrant and most have excellent red, orange and purplish fall colour. The following are the available hybrids (sorry I don’t have pics of them all but my collection is still growing!):
‘Northern Lights’ – the hybrid that started it all. This one has pink flowers on a shrub to 8 feet tall, making it among the tallest of all the series. It was released in 1978.
‘Pink Lights’ – medium-pink flowers of medium size on a shrub reaching to 8 feet. This hybrid was developed in 1984. Unfortunately, it has proven difficult to propagate so is hard to find.
‘Rosy Lights’ – a deeper pink selection from the same cross that created ‘Pink Lights’. It is very floriferous and more compact than ‘Pink Lights’, to 5 feet.
‘Orchid Lights’ – a compact hybrid using R. canadense as one of the parents. The flowers are the smallest of the Northern Lights but the plants are among the hardiest, known to survive to -40 F (-40 C). Plants form thick bushes to 3 feet. This hybrid was developed in 1986.
‘Lemon Lights’ – clear yellow flowers on a shrub that reaches to about 6 feet. Their flowers are reasonably large. It was released in 1996.
‘White Lights’ – from pale pink buds open white flowers with the slighest hint of pink. Plants are sturdy and reach to 5 feet. It is the second hardiest in the group, next to ‘Orchid Lights’. It was released in 1984.
‘Mandarin Lights’ – deep orange flowers, similar to those of the famous Exbury hybrid, ‘Gibraltar’. The trusses are fairly large and plants reach 6-8 feet. It was released in 1996.
‘Golden Lights’ – orange-yellow flowers of a good size and substance. Plants reach to 4-6 feet. This hybrid has the best mildew resistance of any Northern Lights azalea. It was developed in 1994.
‘Northern Hi-Lights’ – a lovely two-toned flower; pale creamy-yellow to white with a prominant yellow blotch. The flowers are medium sized and plants reach to 4-6 feet. This hybrid arose from the same breeding stock as ‘Golden Lights’ and was also developed in 1994.
‘Spicy Lights’ – pink flowers with orange overtones make this hybrid one of the loveliest of the series. Plants reach 5-6 feet. It was released in 1987.
‘Apricot Surprise’ – unusual in the series, this hybrid was not named ‘Lights’ as were the rest. Plants are compact (3-4 feet) with small, often doubled flowers of a distinct apricot-peach tone. This hybrid also has a delightful scent. It was released in 1984.
‘Tri-Lights’ – a newer hybrid developed in 2003. The flowers are white with deep pink edges and a yellow blotch. It is not quite as hardy as the others in the series but has one of the strongest fragrances. Grows 4-6 feet.
‘Western Lights’ – a very recent introduction, this is a tetraploid version of ‘Orchid Lights’. Plants look the same except the flowers are larger with more substance.
‘Lilac Lights’ – a new hybrid developed in 2005 from ‘Orchid Lights’. It has better mildew resistance than its predecessor.
‘Candy Lights’ – another new 2005 release, this one has flowers in a blend of white and light pink. Plants reach 3-5 feet.
If you are looking for the best Azalea and Rhododendron varieties, this list will tell you the ones that are the easiest to grow, most fragrant, and have the prettiest flowers.
Every time I go through my garden to take pictures, I realize that I’m a bit of a plant hoarder. If I like a particular species of plant, I collect a lot of them!
And Rhododendrons (including Azaleas) are one of those shrubs that I love to have in my garden…beautiful blooms, many are evergreen and like shade, some are fragrant, and all are easy to maintain. For me, they are the perfect plant!
So having grown a lot of them, I do have some favorite Azalea and Rhododendron Varieties, and I thought I would share my list in case you are looking to add to your Rhododendron collection as well.
Easiest to Grow – Rhododendron catawbiense
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Zone: 4 – 8
Size: 6′ wide, 8′ to 12′ high
These are the ones that I grew in my first garden, and it turns out they’re a good variety to start with. They are evergreen and have large balls of flowers in the spring…and they’re pretty hard to kill.
In fact the American Rhododendron Society describes these Rhododendrons as “iron clad”…I think that’s about as tough as it gets 🙂
They can also get quite big, so make sure to put them in a spot where they have room to spread out.
Rhododendron Pomegranate Splash*
And they come in a whole range of colors like this one with red-edged white flowers. You can find it HERE.*
Best Compact Rhododendron – ‘PJM’ Rhododendron
Zone: 4 – 9
Size: 4′ wide, 4′ high
The ‘PJM’ Rhododendron is a compact variety that is also quite easy to grow and does better in full sun that most Rhododendrons. It has evergreen leaves and lavender flowers, and provides structure to a perennial border.
PJM Rhododendron ‘Amy Cotta’*
‘Amy Cotta’ is a new version of the PJM Rhododendron that has lavender pink flowers. You can find it HERE
Best Cold Weather Plant – Northern Lights Azaleas
Rosy Lights Azalea*
Zone: 3 – 7 (although some gardeners report growing them in zone 2)
Size: 4′ wide, 6′ high
The Northern Lights azaleas were bred at the University of Minnesota specifically to withstand cold temperatures. They are deciduous azaleas with pretty spring flowers that may be fragrant (depending on the cultivar) and have leaves that turn bright red in the fall.
With so many things going for them, I think they shouldn’t just be relegated to the cold 🙂
The Best Re-Blooming Bushes – Encore Azaleas
Encore Azalea ‘Autumn Twist’*
Zone: 6 – 9
Size: 3′ to 5′ wide and high
Encore Azaleas are a relatively new group of evergreen bushes that bloom twice every year…once in the spring and once in the summer to late fall.
Although they are advertised as a bush that should be planted in full sun, I have them growing in all conditions – full shade, part shade and full sun, and they seem to do quite well everywhere!
My very large Encore Azalea
And as you can see from the picture, they can get bigger than the 5′ height that the label specifies. That arbor in the background is 8′ high.
You can find it HERE.*
Double Pink Bloom-a-Thon Azalea via Proven Winners
There is also a new re-blooming variety called Bloom-a-Thon Azaleas that have very pretty double flowers. I haven’t tried them yet, but plan to add one of these to my garden, also.
You can find them HERE.*
Showiest Blooms – Amelia Rose Azalea
Amelia Rose Azalea*
Zone: 7 – 9
Size: 6′ wide and high
The blooms on the Amelia Rose Azalea are so big and full, they almost look like roses.
Except they grow on an evergreen plant that doesn’t have any thorns!
These Azaleas can be a little hard to find, but I think they’re definitely worth the search!
You can find it HERE.*
Most Fragrant – Rhododendron colemanii
Zone: 6 – 9
Size: 6′ wide, 8′ high
This deciduous Azalea is a native to the Southeastern United States and has the most beautiful scent. It also has really pretty flowers that start out as pink buds and then open to be white flowers with a yellow stripe.
I found it at a local nursery that sells native plants, and haven’t been able to find an online source yet.
Best Variegated Foliage – Bollywood Azalea
Bollywood Azalea, via Proven Winners*
Zone: 6 – 9
Size: 18″ wide, 24″ high
I recently found this compact, variegated Azalea while I was browsing plant pictures online. And I just had to have it.
I had never heard of a variegated Azalea so I wasn’t sure how it would turn out. But I’m happy to report that it is doing very well in my garden!
You can find it HERE.*
I told you I was a Rhododendron fanatic…I can’t even get through creating a list of them without finding another one to buy 🙂
That’s the list of my favorite Azalea and Rhododendron varieties. Hopefully you have found one or two you want to add to your own garden.
More Rhododendron Information You Might Like
- Rhododendron Care: How To Grow Beautiful Rhododendrons and Azaleas
- Rhododendron Problems: What’s Wrong With My Rhododendron?
- Other Shrubs That Thrive in the Shade