Rhododendron Not Blooming: Why Rhododendron Bushes Do Not Flower
Blooming rhododendrons look like colorful, puffy clouds floating through the landscape, so when they don’t deliver, not only is it a huge disappointment, but a cause for concern for many gardeners. No blooms on rhododendrons is rarely caused by anything serious, though, and with a little gardening know how, you can easily get a rhododendron to bloom. Read on to learn what can be done for a rhododendron not blooming.
When Rhododendron Bushes Do Not Flower
Like many plants in the landscape, rhododendrons have very specific needs that must be met before they will bloom freely. If your plant set buds, but didn’t bloom, the buds were probably frost-nipped or destroyed by cold, drying winds. More commonly, though, buds aren’t set at all, guaranteeing non-flowering rhododendrons the following spring.
Among problems of rhododendron, not blooming is one of the easiest to cure. Here are the most common causes and some solutions:
Not Enough Light. Although we commonly plant rhododendrons in the shade in North America in order to keep their feet cool, you’ve got to find a balance between shade and light. Not enough shade may overheat the plants, but not enough light and they’ll lack the ability to produce the energy they need for blooming.
Too Much Fertilizer. Feed your rhododendron all you like in the spring, but by late summer, you need to cut back on both fertilizer and water to give the plant just enough stress to encourage blooming. Always watch the amount of nitrogen you’re giving your plant if it seems to be growing lots of new leaves without producing any flowers – it’s a sure sign you need to back off the feeding. Phosphorus, like bone meal, can help offset this.
Age of Plant. If your rhododendron has never bloomed before, it may simply be too young. Every variety and species is a little different in this regard, so confer with your nursery workers and find out if the rhododendron you purchased is simply a late bloomer, so to speak.
Bloom Pattern. Again, the species of your rhododendron matters! Some species simply don’t bloom every year, or will bloom heavily one year and need another to rest before doing it again. If your rhododendron went to seed last season, that can also have an influence on blooms – watch for next time and remove any dying blooms you find before they can become seed pods.
rhododendron not blooming
My best advice is to pay the relatively paltry amount of money required to hire a landscape architect to draw up a plan. If you do the hands-on work yourself, the cost for the actual plan shouldn’t be prohibitive and will likely save money in the long-run. They consider so much more than plants and shrubs. In our first (newly built) home, hubs and I just couldn’t figure out how to lay out our front beds. We finally contacted a local landscape architect who — keeping in mind that this was about 30 years ago — came to our home, chatted with us, went away to do his magic, and brought back THE perfect plans for the entire front of our home for $125. Did it again in our second home, where it was about $300 give or take, for front and rear (pool area) plans. Probably costs more now, but worth every penny. You might even contact nearby (or zone comparable, anyway) schools with landscape architecture programs to ask professors about recommending a promising (and more affordable) student there. Might even do it free for the experience. Anyway, hubs and I then bought our own plants and shrubs according to the plans, and implemented all ourselves to save money. If you choose not to go with a pro’s plan, then I agree with poster "ianblue" that the plants are actually far less important than overall design, curves, and flow changes. Personally, I would first use paint the foundation the dark hue. No brainer. Next, I’d use a garden hose to lay out a much larger, sweeping border line like the one in ianblue’s picture, marking it with simple dark steel edging for now. (You can always upgrade edging down the road if you’d like). Then, I’d waste no time in removing that straight sidewalk to replace it with one that CURVES down (and possibly toward the drive). Seriously, the house screams for it. As to the walk demolition, I wouldn’t think it would be overly pricey (although the curving redo might be) but I’ve never priced it. That said, if a pro jackhammer removal is too costly, try craigslist? I mean, seems like it’s a simple matter of concrete, muscle, jackhammer, and removal truck, but someone who knows might school me on that. Regardless, it will give authenticity to your home’s Tudor heritage as well as make the house pop. Then, with the concrete gone, you can just sod new grass where the walk was, and if the money isn’t there at that point to add the new curving walk, then just use a stepping stone trail to the drive until you’re financially ready. Those 3 things alone, with no other changes at all, would make a huge, HUGE difference in your elevation, even if the outlined beds had nothing AT ALL in them but basic soil prep for future plants. This is, I suspect, what ianblue was trying to express: design changes first, plants last. Otherwise…I vote no to the terra cotta (but perhaps some other color besides dark brown?); yes to painting the downspout; no to "shudders"; yes to window box on front AND left side of house (kitchen?) but making them slightly longer than the windows, slightly taller than I see here, and quite a bit wider in terms of depth from house; no to the cherry in front of the window or fireplace–rule of thumb is that trees should always frame a home rather than disrupt the view of it; and yes, I emphatically agree with poster "bellburgmaggie" on use and placement of evergreens (plus at least one large and lush fir, staple of any Tudor), on extending the beds around the side of the house (and far side of drive if possible), on the trellis over the drive whenever feasible, and to an overall English garden look, all of which have traditionally complemented Tudor architecture so beautifully. Oh, and whenever the occasion arrives down the road that your roof has to be replaced, I’d go dark instead of light. Probably a deep, deep brown. And my last piece of advice? Take a deep breath and remember that it all doesn’t have to happen this month, or this year, or even this decade. Think in terms of stages. Your home is so pretty, and has the potential to be an absolute show-stopper someday. For now, though, the key is to figure out your **ultimate** front elevation goals. Only then can you determine the order in which things need to be done, the costs, what you can do yourself, what needs to be done by others, and a general timeline for doing it. Starting with plants is putting the cart in front of the horse, which I’m afraid you and the horse–or house–will almost surely regret later. JMO, FWIW.
We have lots of rhodies (not sure of the variety, as we didn’t plant them). Only one bush produces flowers, although they all bud as though they are trying to produce flowers. Someone told me to fertilize them and put compost around them, so I did that last fall, and still nothing this spring. Any thoughts?
The usual suspects when rhododendrons fail to bloom are dense shade, drought or overfertilization. Some sources also say rhodies need careful and thorough deadheading to bloom their best, although I’ve seen many rhododendrons in near-abandoned gardens that are never deadheaded, nor fertilized, and still bloom just fine.
While we think of rhodies as shade plants, they do need light and some sun to set bud and open flowers. Experts at Oregon State University recommend fertilizing with a 10-6-4 formula (more nitrogen than used to be suggested for rhodies), once in February or March before the plant blooms, and again after bloom in June or July.
Rhododendrons have suffered from drought in recent years, because they prefer to be constantly moist. In spring, the plants use large amounts of water for new growth and flowers. Since their evergreen leaves can create an umbrella that sheds the rain, the poor plant’s rootball remains dry and the flowers suffer. If a plant hasn’t received sufficient water, the buds might fall off without opening, which sounds like what might be happening to your rhodies.
So, water them regularly and thoroughly, paying special attention not only during summer drought but also in springtime; fertilize sparingly twice a year; top-dress with compost (but not too thickly, as rhododendrons have shallow root systems); make sure they’re getting some sun, and your rhodies should bloom again next year.
I separated my irises two years ago, and they haven’t bloomed since. The green leaves get tall, but no blooms.
I consulted Brian Thompson, iris expert and librarian at the Miller Library at the Center for Urban Horticulture. He says your iris problem suggests the plants are receiving insufficient light, especially if the leaves are taller than normal (stretching for the light). But some iris varieties are just slow to reestablish. Also, while some early varieties already are in bloom, many later ones have yet to show buds but still should bloom this spring. For more help, Thompson recommends the King County Iris Society’s bearded iris culture page at: www.kcis.org/kcisbeardedculture.htm.
Valerie Easton also writes about Plant Life in Sunday’s Pacific Northwest Magazine. Write to her at P.O. Box 70, Seattle, WA 98111 or e-mail [email protected] with your questions. Sorry, no personal replies.
When to Prune: Typically, rhododendrons and azaleas are pruned after they bloom. This preserves the current seasons bloom, and allows time for the plant to produce flower buds for next years bloom. Rhododendrons and azaleas set next year’s flower buds by mid to late summer. Pruning branches after buds are set removes next year’s flowers. Rhododendrons and azaleas send out new growth after they bloom or after a branch is pruned. Late summer or fall pruning is not advisable as new growth may not be hardened off prior to first frost and may be subject to damage. Some rhododendrons that bloom very heavily can be pruned prior to bloom to reduce the number of flowers and thus maintain plant vigor.
Clean-Up Pruning: Removal of dead, diseased or damaged branches can be done at any time. Tools to use depend on the size of the branch, small branches can be removed with a pruning shear, larger branches require a lopper or pruning saw. Broken branches should be cut just above a dormant bud. Dead branches should be cut back to a branch point, where dormant buds can send out new growth. Interior branches that do not get any light may be removed, because they will eventually die. Diseased branches should be pruned well below any diseased area and disposed of in the trash bin.
Shape Pruning: Pruning for shape enhances the rhododendrons form and habit. All rhododendrons can be pruned to maintain their natural habit, but to try to keep a tall growing rhododendron small or low growing is not practical. Tall, leggy plants should be replaced with smaller varieties or plants having a low, mounding growth habit. If a plant grows out over a walk or needs to be restricted for some reason, it may be pruned back moderately without fear that the plant as a whole will be damaged. Remove weak or crossing branches. This provides improved air circulation and removes branches susceptible to disease and insect damage. Rhododendrons should be pruned just above a growth bud. Don’t leave short branch stubs which will die and can become an entry point for disease.
Evergreen azaleas can be sheared for hedges or borders. Unlike rhododendrons, evergreen azaleas can be sheared each year after flowering to create a densely-shaped plant. Deciduous azaleas can be cut anywhere on the stem and they will branch from that point, though they should not be sheared as severely as evergreen azaleas. Pinching or shearing the new growth can induce branching. Timing is important if optimum results are to be achieved. If new shoots are pinched too early the likely result will be a single new branch replacing the nipped growing point. If pinching is done at the right time several buds will break below the point pruned. Early summer is usually a good time for shaping azaleas.
Rejuvenation Pruning: As rhododendrons age they lose leaves and often become open and very leggy. Rejuvenation pruning, can be useful to reshape a plant. By pruning just above viable dormant buds, new healthy growth can be directed to obtain a more desirable shape. The larger-leafed rhododendrons have many dormant buds that can be forced into new growth. However, on very old wood, the dormant buds may have atrophied and are not viable. So there is some risk that drastic pruning may not be successful. A safe procedure is cut out about one-third of the old wood spread over a period of three years. In this way, there remains sufficient leaves to supply nutrients to keep the plant growing successfully each year.
Spent Flower Removal (Deadheading): It is desirable, with the large flowered rhododendrons, to remove the withered flower clusters after the blooming season. This is fairly easily done as the central axis of the cluster, usually called a truss, will break free from the plant with a push of the thumb pushing on the side, or can be cut off with a hand pruner. (See photo.) Dead-heading is usually done to make the bush look more attractive, to reduce the prevalence of fungus and to prevent a heavy set of seed. If it is not possible to remove the old flowers, it is usually not too detrimental, but flowering the next year may be reduced. When deadheading care should be taken to not damage the growth buds or new shoots which are located just below the flower cluster.
Spent flower removal. Photo by Steve Henning
More information about how to prune rhododendrons and azaleas can be found in the following ARS articles:
How and When to Prune Rhododendrons by Warren Baldsiefen
Tips for Beginners: How To Prune Evergreen Azaleas by Tom Hughes
Tips for Beginners: Pruning of Rhododendrons and Azaleas by Ted Irving
Pruning Rhododendrons by Bill Stipe
Index of Contents
Propagation & Hybridization
Insect & Disease Control
frequently asked questions
To submit a question or receive a personalised reply please email [email protected] your question will be answered by Marina Shearer – owner of RhodoDirect Nursery.
The Number 1 most asked question – why do some of our rhoda’s leaves go yellow, orange or red?
There is nothing wrong with your rhododendron unless all the leaves are changing colour. It is a very normal part of the lifecycle of the rhododendron for leaves to discolour and fall off. This happens after a leaf has been on the plant for 3 years. It is normal and there is nothing wrong with your rhododendron and you can’t do anything to fix it. Some times of the year it is more noticeable and often it is noticed because it is just a few leaves changing colour. If you want a second opinion then email a photo of your rhodo to [email protected] and we will take a look.
If your whole rhododendron is changing colour to a pale green or yellow then you definitely need to address a nutrient deficiency.
What do I need to grow rhodos?
Free Draining Soil (this can be created by planting rhodos on top of the ground if needs be)
Water and plenty of it, particularly in the heat
Acid soil (you can create it if you don’t have it already)
A canopy of deciduous trees OR plenty of mulch for water retention is a PLUS!
Can I use animal manure on my rhododendrons?
You can use animal manure but be careful not to burn the fibre roots at the top of the rhodos root ball. Instead spread it around well away from the rhodos roots and ensure it is well rotted. For more comprehensive information visit our fertiliser advice page
If my property has late frosts can I plant fragrant varieties?
Nearly all fragrant rhododendrons are frost tender. A good rule of thumb to abide by is if the area they are going in will be affected by a -4 degree Celsius frost, then don’t plant them. Sometimes you might get bad frosts but have a very sheltered location for fragrant varieties to grow, like under the eaves or in a protected part of the garden. A frost will damage the flower buds, and once damaged they don’t recover, they just fall off the plant. Most frosts won’t kill the plant, however, a severe frost will kill the plant too. We recommend that you consider carefully before choosing a fragrant variety. The perfume is magic, but you need to be able to provide good shelter from the frost to enjoy that marvellous perfume.
Do we need established shade from trees before planting?
One of the concerns we hear from customers is that they don’t have enough shade in their garden. Many customers plant trees in their gardens first and think that they will have to wait until the trees have provided shade before they can plant their rhododendrons. This is not the case – no waiting is required if you do it right. Rhododendrons thrive in an environment where their root ball is moist. The feeder roots of rhododendrons are near the surface, no more than 10cm from the base of the plant. It is these roots that need to be kept moist. There are any number of ways of doing this; if you provide one of the following you should do well.
1. A heavily mulched covering around the rhododendron. Leaf matter, bark, pea straw or pine needles are all options. Pine needles have the added advantage of keeping the weeds at bay and of offering acidity that rhododendrons love. The mulch helps to keep the moisture near the roots and ensures that the roots don’t dry out.
2. Shade overhead. Established trees will provide a canopy over rhododendrons which helps to keep their roots moist. This could be either deciduous or evergreen or a mixture. Rhododendrons do need the sun however, and many varieties flower better with sunlight.
3. Water, either by drip or sprinkler or any other system you have. If you don’t have shade or mulch then you will need to keep the moisture up to the roots through watering. However, be aware that rhododendrons like free-draining conditions so ensure that water doesn’t build up in their roots and that the plants are not sitting in pools of water. Note that if a plant dries out completely no amount of water will nurse it back to health.
As you travel around New Zealand you will notice rhododendrons growing in certain environments that you might not recognise as being particularly textbook conditions. Generally, the conditions will have one of the above three points going for it. On the West Coast of the South Island, you will find huge rhododendrons growing in random places, like in the middle of a paddock, or beside an old derelict house where no-one lives. The Rhododendron has thrived probably because of the high rainfall of the West Coast. A large established Cunningham’s white rhododendron grows in a cemetery in Canterbury: no-one looks after it and no-one waters it, but the mulch around it has created an environment where it can not only create enough moisture to survive – it has enough to thrive.
Can we plant Rhododendrons if we have Clay Soil?
Many individuals who would dearly love to grow rhododendrons have steered away from them because of their clay soil. Don’t let having clay soil stop you enjoying a rhododendron garden. If heavy clay is present then dig a small hole and run some water into it; if the water does not disappear in a few minutes then you have poor drainage. This is not a sure test but it will give you a good indication. Sometimes the top soil layer will drain well, but there will be a hardpan underneath it that will not drain well. If you have good drainage your rhododendrons will like it, if you don’t, then you can create a better environment by planting the Rhododendron on top of the clay and not in it.
To achieve the desired result use plenty of mulch, leaf matter, pea straw and pine needles. By elevating your garden and planting your rhododendrons above the clay level you will create an environment where they can thrive.
One grower tells the story of President Roosevelt in his garden that was looking decidedly terrible. In frustration and anger he ripped the Rhododendron out and tossed it up the bank. Expecting his actions to have killed the Rhododendron imagine his surprise when a few weeks later he found the plant had re-established itself in the mulch and was looking better than ever. On noticing this he went around his garden and lifted all the sad looking rhododendrons so that they were now sitting on top of the soil in the heavy layer of mulch.
Update for July 2nd, 2017:
The blooms are here! The areas near Price Lake and south of Blowing Rock on the Blue Ridge Parkway are showing peak bloom on rosebay rhododendron shrubs.
June 22, 2017: They’re nearly here! Lots of people ask about when the rhododendrons bloom, and that depends on species, elevation, and local climate. The Rosebay Rhododendron is about to put on a pretty show in Blowing Rock. The pale clouds of rhododendron along the local section of the Blue Ridge Parkway will soon be beckoning you to pull over. “Stop and smell the roses,” right? The buds are almost ready to break, and a few have begun this week. This photo was taken Monday, June 12, and you can see that there are lots of buds waiting to open up.
The Rosebay, also known as the white rhododendron, is a prominent rhododendron along the Blowing Rock areas of the Blue Ridge Parkway. This particular variety blooms later than similar counterparts found nearby, the Catawba, Carolina, and Piedmont rhododendrons (there are lots of rhododendrons in this area!). The darker, sometimes near-fuschia, blooms of the rhoddies in downtown Blowing Rock and in nearby parks peak in May. Rosebays, which vary from white to very pale pink/purple, typically begin to bloom in mid-June in this area. Now that they have started, we can expect blooms for several weeks.
While there will be some blooms this weekend, it won’t yet be peak viewing time, as many buds are still shut tight. The blooms will still be opening up into early July. Price Park is an excellent location to see large collections of the shrub, and the sheer number of blooms during peak is stunning. Take a hike around the lake on the Lake Trail to get a real immersion into the rhoddie growth, or rent a canoe from the docks and enjoy the blooms from the water. The amphitheater is a nice spot to sit and enjoy, as rhododendron growth surrounds the seating.
Right now, the mountain laurel is still showing impressive clumps of white and pink blooms, though most spots of laurel are just past peak. There is a good collection of them at Sims Pond Overlook and a fair number to enjoy at Price Lake. Though rhoddies are of interest to many visitors, there is always something to see, from flame azaleas in May to asters in September. For a full list of wildflower blooms along the Blue Ridge Parkway, visit the Bloom Schedule page on BlueRidgeParkway.org.
Rhododendrons form new buds during summer; it is most important not to cut any buds off or there will not be any flowers for next year’s display.
I’m sure you are curious about your flowers not blooming; it’s just not time yet. But, there’s always an exception! If we happen to get a warming trend, some buds will open. Occasionally if the weather is extremely cold, buds may freeze and not survive well for the coming spring flowering show.
Water well at least once a week during the growing season and add pine bark mulch to conserve moisture. Keep plants watered during warm winter weather. If we get enough rain once a week that may be sufficient so you don’t have to water.
Compost laid on top of the soil yearly in spring is always helpful to condition the soil. Once the ground is frozen, and you didn’t get to mulch around your shrub, you can mulch while the ground is in a deep freeze state. Rhododendrons like acid soil and part shade.
If you have any more questions let us know. There’s more below from the Rhododendron Society linked below.
Hope this is helpful.
Courtesy of NYBG Plant Information Service
Rhodies Go Wild
The special virtues of species rhododendrons By Steve Hootman, Co-Executive Director, RSBG
RHODODENDRON ORBICULARE: Thrives in the cool summers and mild winters at the RSBG. Native to the remote misty mountains of the Wolong Giant Panda Reserve in Sichuan, China, where it flourishes deep in the forests alongside bamboos. Photo by: Andrew Drake.
For diversity of size, form, foliage and flower color, it is hard to imagine any other group of plants matching rhododendrons and azaleas. We all know about the spectacular garden hybrids with their blinding colors and huge flower heads. But there is another remarkable group known as species rhododendrons, wild plants found growing naturally in the forests and mountains of the world, many of which make outstanding garden plants. One of the best places to see them is the Rhododendron Species Botanical Garden in Federal Way, Washington, which contains one of the largest collections of rhododendrons worldwide.
AppealThousands of variations with a virtually unlimited palette of floral color blooming from late winter into late summer. Some types are fragrant. The foliage of many species is extremely unusual and attractive, providing year-round interest.
ZonesEasy to grow in cool-summer/mild-winter regions, Zones 5 to 9. Outside of these regions, it is still possible to grow many kinds if care is taken to select the appropriate cultivars or species. The RSBG is considered Zone 8.
ExposureIn general, rhododendrons require a bright but not-too-hot exposure with low soil temperatures. Exceptions are the tiny-leaved alpine and dwarf species, which are best in bright sun.
RHODODENDRON DAVIDSONIANUM AND R. AUGUSTINII: Two of the finest and easiest species to grow in their color classes, the deep pink of the former contrasts brilliantly with the lavender blue of the latter. Photo by: Andrew Drake.
SoilExcellent drainage in an organic woodland soil or in a sandy soil that has been amended with bark or other organic matter. In heavier and clay soils, plant in raised beds.
CareWater through dry periods. Regular mulching with organic material means extra fertilizer is usually unnecessary. If the plants seem unhealthy, it is usually because of poor drainage.
DESIGNING WITH RHODIES
- Think mobility. Because of their fibrous root system, rhodies are easily moved as conditions warrant.
- Grow with ferns and wildflowers, which appreciate the light shade under rhodies.
- Plan for a long season. It’s possible to have species rhododendrons in flower from the earliest thaw of spring to the longest days of summer.
- Fit rhodies to the space you have. Most can be selectively pruned to reduce their size. Better yet, select the right-sized or even dwarf plant for the site.
- The subtle coloring of species rhododendrons is easier to integrate into the garden than the often harsh colors of hybrids.
Read on to discover a collection of wild rhodies that make outstanding garden plants:
Photo by: Andrew Drake.
Easy in sun or shade, this species is slow-growing enough to cultivate as a specimen in a large container.
Photo by: Andrew Drake.
Large-growing species with lavender-blue flowers, suitable for sun or shade. It can be selectively cut back to reduce its size. Selected forms have flowers closer to true blue than almost any other rhododendron. Hardy to 0 degrees.
Photo by: Andrew Drake.
Famous flame azalea native to the forests of the Appalachian Mountains. Brightly colored blossoms occur naturally in blazing shades of red, orange and yellow. Tough, hardy, deciduous species well-adapted to gardens, performing beautifully in sun or light shade. Hardy in Zones 5 to 8.
Photo by: Andrew Drake.
RHODODENDRON DEGRONIANUM SSP. YAKUSHIMANUM
A perfect garden plant and probably the most popular and widely grown species in the world. Native to Japan with a dwarf mounding habit to 3 feet, foliage that is densely hairy or “indumented” on the leaf undersides and perfect apple-blossom-pink flowers fading to pure white. Used extensively in hybridizing programs. Relatively cold and heat tolerant. Hardy to -15 degrees.
Photo by: Andrew Drake.
Extremely variable, native to Japan, and, like many plants from that region, it is well-suited to cultivation in East Coast gardens. The pale yellow flowers of the larger growing forms shine in the woodland garden, while a diminutive selection known as ‘Yaku Fairy’, from the mountainous island of Yaku Shima, is the perfect dwarf for a rock or trough garden.
Photo by: Andrew Drake.
Vigorous and bushy, native to Sichuan, China, extremely floriferous. Does not require the removal of spent-flower trusses-known as deadheading. Lovely flowers range in color from pale pink to lavender or mauve, often with dark red spots. Hardy to about 0 degrees.
Photo by: Andrew Drake.
Always attracts attention with its smooth round leaves and rose-to-pink bell-shaped flowers. Best in light shade to maintain the mounding habit and avoid foliage scorch. Hardy to -5 degrees in maritime climates.
Photo by: Andrew Drake.
One of the best of the dwarf or “alpine” rhododendrons for the rock garden. Easily grown in a sunny location with excellent drainage, this species forms a dense mound to 3 feet with striking blue-purple to reddish-purple flowers. Native to southwest China. Hardy to -15 degrees.
Photo by: Andrew Drake.
Variable species native over a wide area of Japan, with different forms occurring on virtually every mountain range in the southern half of the island chain. Lower surface of the leaves is coated with a dense furry layer of hairs known as the indumentum, adding welcome color and interest in the nonblooming season. Pink to rose or rarely white flowers appear in late spring, and the plants are quite adaptable in most climates, even tolerating the heat and cold of the East Coast and upper Midwest if provided with proper shade and care. Hardy to -15 degrees.
Photo by: Andrew Drake.
Deciduous azalea, outstanding as an ornamental for a sunny border or woodland edge. Bright yellow flowers are delightfully fragrant, and autumn foliage brings a bright red splash of color. A clone selected at the RSBG known as ‘Golden Comet’ is an especially fine form with a much larger inflorescence of deep yellow flowers and good resistance to the common, disfiguring but relatively harmless powdery mildew that so often afflicts azaleas. Hardy to -10 degrees.
Photos were taken at the Rhododendron Species Botanical Garden, south of Seattle, Washington. For further information on rhododendrons and the garden, call 253-838-4646 or see www.rhodygarden.org.
Related: Viraya Rhodedendrons
Rhododendrons in Bloom
JOHN PATRICK: I’m at the National Rhododendron Gardens at Olinda in the Dandenong Ranges just a short distance to the east of Melbourne. This spectacular 40 Hectare site was established in the 1960’s and now has over 15,000 Rhododendrons, plus another 12,000 of that closely related plant, the Azalea.
Rhododendrons are mainly Northern Hemisphere, cool climate plants and they’ve been grown in European gardens since the 17th Century. But the range available to gardeners increased dramatically in the 19th Century when Europeans visiting central Asia and returned home with spectacular species and now there is incredible variety with over 28,000 Rhododendron forms available today.
And this is the type of plant that would have inspired those early European collectors in the Himalayas, with its wonderful large trusses of bell-shaped flowers. They’d never seen things like this before so it was absolutely fantastic to be able to collect them and take them home. And you’ve got to remember the word Rhododendron means ‘Rose Tree.’ These grow to be big plants and they’re really dramatic in their native habitat.
Traditionally, Rhododendrons were selected for their flowers, but many of them have remarkable foliage too and because it’s evergreen, it can contribute to your garden throughout the year. This one is one of the ‘Grande’ group and it has pendulous foliage designed to shed heavy snowfalls in its native habitat. By contrast, over here, is aRhododendron williamsianumwith a much smaller, neater leaf.
Another particularly endearing foliage quality of some Rhododendrons is the indumentum underneath their leaves. It’s a most beautiful soft furry quality. This particular one isRhododendron elegantulumand this soft indumentum is thought to be a means by which they can collect atmospheric moisture, so that when the roots dry out, they can take moisture in through their leaves.
Rhododendron flowers vary enormously in size and shape. These ones onRhododendron leucaspisare small bells and it’s the bell form which is typical of Rhododendrons. Some are in big heads, large bells, some have elongated bells. You can choose a different sort to suit your taste.
In the home garden, it’s the smaller growing species and forms that are likely to be chosen, but remember, as you get right down in size, many of the really small Rhododendrons are probably from high altitude areas, where they’re in tune with cold environments. That makes them quite difficult to grow in hot, dry conditions, though they will grow in pots and of course you can move those as needs be to suitable places in your garden.
In the contemporary home garden, the Rhododendrons with the most potential for use are the Vireyas. Now these come from tropical parts of the world at high altitude and they’re well able to tolerate humidity as well as cool temperate conditions.
Now the great joy of these plants is their spring flush of tubular flowers – the most wonderful clean, clear colours. They also continue to spot flower during the summer, so it extends the traditional flowering display.
Rhododendrons perform best where soil pH is around about 5. They enjoy protection from the hottest sun and perhaps most importantly, they appreciate summer moisture, so keep those roots well watered. If you do that and choose a form that’s right for your garden, they’ll reward you with wonderful displays of spring colour – such a welcome thing after the dark of winter.
STEPHEN RYAN: Well that’s it for this week, but if you’d like to know more about Angus’s visit to Brenda’s wonderful garden, you can read all about it in the October Issue of the Gardening Australia Magazine. But now, let’s have a look at what we’ve got lined up for you in next week’s program.
Josh is in Perth looking at some spectacular Western Australian wildflowers in King’s Park and suggesting some that might be good for the garden.
Tino’s back in The Vegie Patch with some invaluable tips on how to grow great tomatoes and he gives us the results of his seed versus seedling experiments.
And Angus joins a gardener who’s just mad about her Clivias – or should I say Clivias? You’ll have to wait till next week to find out.
I hope you can join us then and in the meantime, let’s get outside and enjoy the garden.