- Diseases Affecting Viburnum: Learn About Viburnum Disease Treatment
- Common Viburnum Diseases
- Viburnum x bodnantense ‘Dawn’ is a superbly scented shrub that produces its fragrant clusters of flowers on a bare and leafless plant.
Diseases Affecting Viburnum: Learn About Viburnum Disease Treatment
Viburnums have layered branches that are coated in spring with lacy, delicate and sometimes scented flowers. They are remarkably tough plants and suffer from few pest and insect issues. There are more than 150 species of Viburnum with many available for problem areas of the garden. Plants that are not well taken care of, however, can occasionally develop viburnum diseases, primarily fungal issues, especially if circulation is not provided.
Common Viburnum Diseases
Viburnum shrubs are very adaptable plants. That means they rarely have any disease issues. Common viburnum bush diseases encompass those caused by fungus, while other disease issues are rare. In most cases, correct siting of plants, adequate air circulation and good watering practices can prevent these soil or air borne problems. Plants under stress are most prone to lasting damage from these types of illnesses.
The most prevalent diseases affecting viburnums are fungal diseases of the foliage.
- Powdery mildew affects many types of plants, from ornamentals to vegetables. It is characterized by fine white dusty growth on the upper surfaces of leaves.
- Downy mildew causes leaves to develop splotched areas which die and shrivel in spring. It is most common when the weather is wet.
- Fungal leaf spots are caused by a different fungus, Cercospora or sometimes Anthracnose. Spots on leaves begin small but gradually develop. The area is angular and irregular and may be reddish to grayish brown. These tend to occur in warm, wet summer months.
The viburnum disease treatment for these types of plants is all the same. Avoid overhead watering, apply fungicide if the disease is rampant and destroy damaged leaf material.
One of the most damaging diseases of viburnum is Armillaria root rot, also known as shoestring root rot or mushroom root rot. This is another fungus, but it affects the roots of the plant and can lead to death. Initially, the leaves and stems of the plant will appear stunted, yellow and leaves may drop to the ground. As the disease works on, the roots of the bush will gradually get sicker and sicker. The process can take several years but eventually the tree will die.
It can be hard to diagnose, as symptoms mimic other stresses such as lack of water or poor care. The upper crown and roots of the plant will pinpoint the cause if examined, however, and white fungal growth will be visible under the bark. If the root system is diseased and making its way into the trunk, the plant cannot be saved. This is one of the most dangerous of the viburnum bush diseases.
Bark and branches
Botryosphaeria canker is a serious disease of viburnum and many other ornamentals. It is characterized by dead or wilted leaves. The fungus produces fruiting bodies that show up on bark and branches as brown to black, plump bumps. Bark becomes dark brown. The fungus gets into the plants through some injury and destroys the cambium. Cankers form, which girdle the tree, effectively cutting off nutrients and water movement.
Drought stressed bushes are mostly affected. Prune off affected material with sterilized pruners and provide consistent water and fertilizer over the season. There is no viburnum disease treatment for this ailment, but once the plant gains health, it can usually withstand the fungal attack.
The distinctive scent of Korean spice viburnum can stop you in your tracks during an early May stroll: sweet, rich, and complex with a hint of cloves. You may encounter it in the Sensory Garden, in the English Walled Garden, or in other garden byways.
Wise gardeners plant this shrub near a path or doorway to enjoy the full effect during the two weeks or so when its small white flowers, opening from pink buds, are most fragrant. Korean spice viburnum (Viburnum carlesii) also offers an attractive wine-red fall foliage on a compact, spreading 4- to 5-foot-high shrub.
It’s just one of the hardy, adaptable viburnums, a group of easy-care shrubs that bring bloom, fruit, and fall color to many a midwestern backyard. Many of them have fruit that attracts birds and may persist most of the winter.
Viburnums tend to prefer slightly acid soil, but a number of species easily handle the alkaline conditions of many Chicago-area yards. They have few pest or disease problems and need little pruning, if they are properly chosen and planted in the right place. As with all shrubs, it’s far easier in the long run to select a species or variety that you will have room for when it has grown up than to try to control a too-big plant with constant pruning.
Most viburnums do best in full sun, but arrowwood (Viburnum dentatum) can tolerate part shade. As its common name suggests, the straight stems of this upright American native were once used to make arrows. The broad white flower clusters that come in June are fragrance-challenged, but they mature into blue-black berries that birds love.
The glossy, sharp-toothed leaves often turn deep red in autumn, depending on the weather. Northern Burgundy (Viburnum dentatum ‘Morton’) and Autumn Jazz (Viburnum dentatum ‘Ralph Senior’) are selections from the Chicagoland Grows program chosen for more reliable fall color, among other good qualities. Arrowwood is a big shrub, often reaching 10 feet high and wide, so give it lots of room.
Another substantial viburnum is the especially adaptable wayfaring tree (Viburnum lantana), which grows well in alkaline soils and tolerates drought. Despite the common name, it usually grows as a rounded, multistemmed shrub that can be 10 to 15 feet high and wide. It has 5-inch-wide flower clusters that, alas, have scant scent. But they become berries that ripen, often in a multicolored display, from yellow to red to black. The rough-surfaced leaves are bluish-green until they turn gold to red in autumn. ‘Mohican’ is a somewhat smaller cultivar — it tops out at about 10 feet — with berries that are bright red for a month before ripening to black.
If you want a downright tree, one that can reach 30 feet in a couple of decades, the native blackhaw (Viburnum prunifolium) can be trained that way. It has creamy flower clusters in May and pink fruit, eventually ripening to black, that is edible by humans as well as birds.
The most elegant of these shrubs is doublefile viburnum (Viburnum plicatum f. tomentosum), with stately horizontal branches on a 10-foot-tall shrub. ‘Mariesii’ is the cultivar most known for its layers of broad, flat, white flower clusters, though it bears little fruit. The crinkled leaves are bright green in spring, deeper green in summer and usually burgundy in autumn.
Doublefile viburnum is not quite as hardy as some other viburnums, but in a sheltered spot it often does quite well. Plant it as a specimen with plenty of room to show off its fine form.
A lovely native species is American cranberrybush viburnum (Viburnum trilobum). Shiny red fruits follow the white flowers if they are pollinated from another plant, and broad leaves, almost maple-shaped, turn bright red in autumn. Redwing (Viburnum trilobum ‘J. N. Select’) is a cultivar with a relatively dense form, growing up to 10 feet tall and 8 feet wide.
What if you don’t have that kind of space? The Judd hybrid viburnum (Viburnum x juddii) is a bit smaller, growing only 6 to 8 feet tall, with a rounded form. Its delicate pink-white flowers’ fragrance reveals that Korean spice viburnum is one of its parents. The leathery dark-green foliage often turns red in autumn.
Beth Botts is a garden writer and speaker who lives and gardens in Oak Park, Illinois.
Three years ago I wrote a piece on viburnums. I got a long and angry letter from an older reader berating me for using an unacknowledged quote from Hillier’s Guide to Trees and Shrubs . Quite right, too – although perhaps not quite the proof positive that, as he suggested, I was a charlatan unworthy of ‘this once-great paper’s pages’. But ever since then I have always tried to acknowledge descriptions that were not my own and also to limit myself to writing about what I know. And I know so little. And I have so many books. And I read so much. And – this is the real issue – my own garden here in Herefordshire is deliberately and inevitably very limited to what we like and to what will grow happily in our wet climate and heavy clay loam.
I have a problem with winter-flowering shrubs. I don’t mean the early-spring-flowering ones such as the daphne, witch hazel, forsythia or winter-flowering jasmine. I like them as much as for their being harbingers of spring as for their flowers. Nor do I mean the latecomers, such as the few roses that will flower on to Christmas, especially when helped along by global warming. But this no-season’s land between Bonfire Night and Christmas, or not-autumn and not-quite-winter, is a season of coloured leaves, coloured barks and berries. Leaves are valued mainly in their passing. If they stayed half-alive and half-dead for more than a few weeks, we would soon be tired of them. Likewise berries, which are so shinily un-flowerlike that they are another completely new instrument playing the old tune. And bark is perfect for winter. The more coloured stems we have in this garden the more I want. It suits the season.
Each of these things is lovely on its own and well orchestrated, and they can enrich a poverty-stricken time. But no plant, at this stripped-out time of year, provides flowers in scale, form or colour that warrants space in the garden. I can look them all up, know a fair bit about them and can collate all that knowledge for you, but it does not really convince me. There is something about a lone-flowering shrub on a wet winter’s day that seems rather futile. However lovely the plant, it often fails to do enough. The lesson is not to ditch them but to think carefully about their positioning. They are not at their best in a border that is geared for summer display.
Nevertheless it would be less-than-optimistically human to abandon the precious few flowers that we do get in midwinter just because they don’t quite work in the garden. I realise that for most people they have a powerful magic. The few times I have seen really effective use of winter shrubs, they have been tucked into a corner or in the lee of a wall or by a door or window. They need to be used as a vignette, not a statement, because there is too much sky and, with a few exceptions, the statement is lost in the wind, rain and muddy grey of a winter’s afternoon. Keep it cosy.
The viburnums are the biggest and best-known group for this. I had dinner with a garden-designer friend the other day who told me that when he started out and was asked the name of a shrub that he did not know – and one of the surest rules of life is never trust anyone who can instantly name every plant in any garden – he would reply, ‘Viburnum.’ It worked every time. The reason for this is that it is such a large and diverse family, ranging from the most familiar of the lot, Viburnum x bodnantense ‘Dawn’ with its floret bubbles of tiny flowers on bare branches that can start appearing now and last right through to March, to the evergreen V tinus ‘Laurestinus’ or the spring- flowering Viburnum plicatum ‘ Mariesii’ that looks like an exceptionally lovely hydrangea. Viburnum farreri has a good fragrance and is best outside against a warm wall that will trap its scent. The species flowers are white, tinged with pink, whereas V farreri ‘Candidissimum’ is pure white. V tinus has no scent but the distinction of black berries, while V x bodnantense ‘Dawn’ smells, according to my letter writer (telling me a little more than I wanted to know) like cat’s pee. It doesn’t.
I have been trying to think of ways to make these shrubs work, to improve them, and it cannot be done. The truth is that I think these are dull plants and belong to dull gardening. In the summer they are hopeless and in winter, for the most part, their flowers are a token, rather like the Christmas present that you do not want. You appreciate the thought but_ They stem from a lazy view of garden-as-chore, which breeds the notion that a ‘good’ plant is one that covers most space with least work. Think of all the gardens with a strip of token border around the edge and lax shrubs planted too close to the fence dotted without rhyme or reason along it. Either that or think of the approach to an M4 corridor corporate headquarters. Better to fill the body of the garden with shrubs as understorey to a few standard trees – which is what most of them want to do.
I do have a soft spot for wintersweet, Chimonanthus praecox. Like many winter-flowering shrubs, it isn’t much of a looker, but the little primrose-yellow blooms are fabulously fragrant and make very good cut flowers. The scent stays much longer if kept in a cold room. It can be trained to make a climber on a sheltered, sunny wall and, in many ways, is best grown like this, with a clematis using it for support in the summer.
I like mahonias, although I wouldn’t go so far as to plant one in my own garden – no place that feels right for them. I like the way the evergreen leaves and bright-yellow flowers combine a faintly exotic, jungly feel with daffodil freshness. An unlikely mix, but it does seem to work. Mahonia x media is perhaps the best known, with the clones ‘Charity’ and ‘Lionel Fortescue’ very available. All mahonias smell good, but M japonica is perhaps the most fragrant of all. The Asian mahonias like shaded sites and will tolerate a wetter soil than the American mahonias. They are particularly suitable for a thin soil over chalk.
Although I have been dismissive of these scant winter-flowering shrubs, I do grow a couple of varieties of winter-flowering honeysuckle, Lonicera fragrantissima and L purpursii and the evergreen version, L standishii. I somehow acquired them years ago and, tucked away almost entirely out of sight on a north-facing wall, they provide the best-scented of all winter flowers. It is rare for them to flower this early, but there are usually a few tentative tiny flowers by Christmas, and they hit their full stride by the middle of January.
My roots: A week in Monty’s garden
Did I say that we got through the floods unscathed? I spoke too soon. Between writing last week’s words and these, the water has lapped at our door and laps yet. To try to provide drainage, we have dug a trench right down the length of the garden and laid a perforated land drain. It was dug fast, by eye, and curves subtly.
The floods rose again as this was being done and the trench promptly filled to the brim, without making any noticeable difference to the water levels in the garden. The trench was cut down a grass path, but the rain made the sides collapse overnight, so parts of Jewel garden borders had to be evacuated so this could be repaired. While the emergency digging went on, Poppy, our Jack Russell terrier, went on a manic vole-hunt, digging dozens of holes in the borders, spraying tulip bulbs at every pass and destroying the roots of scores of plants. Sort of funny, but also sort of the last straw.
Although the canal/trench is a thing of sinuous beauty, there is a huge amount of soil thrown up from it. This is now completely saturated. An utterly sodden 70m mound of mud. The demarcation lines between grass, flood and mud are indecipherable runes ploughed into the ground.
The truth is that if we knew then what we know now, we would have laid this garden out in a completely different way to accommodate the inevitable flooding. Over the past week, I have toyed with taking a JCB to the place and doing just this, but balk a little at that. If I inspect my motives honestly I have to confess that I feel I have not displayed what we have done enough. I want more TV crews, more public sharing in this place before I rip it apart. Vanity or altruism? Neither, really. Just a natural born show-off.
Despite the waters rising, we have continued the process of cutting four new 2m brick squares into the Jewel garden. This means digging up hard paths, potting up plants, removing topsoil and putting in scalpings and sand before laying the bricks. It is worth the trouble tenfold and has dramatically improved the garden. This garden has always been very long on places to delve and hoe and short on sites to sit and consider, which means that the large beds now revolve around these small seating areas and we can go out and drink our champagne in one of five spots according to the light and state of performance of the plants. Dressed, of course, in waterproofs and waders.
Your roots: Golden rules for prudent pruning
I know that people can get into a muddle about pruning shrubs – as though there was anything to be muddled about.
The first rule of all pruning is: when in doubt, don’t. The second rule is always to cut back to something, be it a leaf, bud or branch. And the third is that winter pruning promotes vigorous spring regrowth . So resist the evidence of your eyes and cut the existing weak growth back hardest.
Notice if the flowers are produced on the current year’s fresh growth or on the previous year’s. If the former, it is best to prune in early spring – as in the case of buddlejia – and if the latter, the time to do it is immediately after flowering – as with ribes.
When you plant shrubs, prune any weak growth hard to encourage good strong shoots from the base of the plant next spring.
If you are growing a shrub for its leaves, as I do with a cut-leaf golden elder, cut it back hard each spring and the new leaves will be both bigger and better coloured than they would be if it had been left unpruned.
Viburnum bodnantense ‘Dawn’:
Viburnum x bodnantense ‘Dawn’ is a superbly scented shrub that produces its fragrant clusters of flowers on a bare and leafless plant.
A leafless shrub covered in flowers in winter is definitely a thing of curiosity and Viburnum x bodnantense ‘Dawn’ is worth a close inspection, with a sweet and delicious scent. The flowers of this shrub are gathered together in clusters hanging from the stems like perfume-filled pompons.
The flowers of Viburnum x bodnantense ‘Dawn’ can appear any time from October to March depending on how cold the winter is. If the winter is mild they can flower early.
Viburnum bodnantense ‘Dawn’:
This shrub is straightforward to grow. It will grow in any soil, so long as it isn’t waterlogged. It can grow to 2.5m in height but if the plant grows too big you can simply cut it back to the ground in spring. It is a good idea to let the plant grow as big as possible so that you can cut some flower stems to fill the house with fragrance, without spoiling the overall look of the plant.
Viburnum x bodnantense ‘Dawn’ gets its name from the Bodnant Garden in Wales where the plants Viburnum grandiflorum and Viburnum farreri were cross bred to produce ‘Dawn’ in the 1930s.
Missed a day of our Advent Calendar? To find out about more classic flowers that look at their best in December,
Viburnum tinus is perhaps best planted on its own, or as a background to other shrubs. You could grow a late, small-flowered crimson clematis through it that can be cut down after flowering. ‘Kermesina’ is the one to seek. The x burkwoodii forms are easier to integrate in mixed borders. If you want to mask the foxy smell of crown imperial fritillaries, try planting them nearby.
- Surpisingly, for it does not seem tender except in very cold winters, laurustinus comes from the Mediterranean, where it grows on dry rocky limestone hills. It does not mind shade, but the flowers will be better in the sun
- You can clip V.tinus, but use secateurs, not shears. ‘Park Farm Hybrid’ and ‘Anne Russell’ can be grown as standard trees and they respond well to clipping.
- All the viburnums mentioned are obliging shrubs on any soil or position, but they do not like to be waterlogged
- Like everything, they will do better if you treat them kindly. Give them a good start with a little leaf mould and enough room to develop.
- If you wanted formal specimens, the ones to clip are V.tinus or x burkwoodii, but on the whole, viburnums need no restraining.
Where to buy
Nationwide garden centres such as Wyevale will stock most of the viburnums mentioned but for the rarer sorts – ‘Winton’ and ‘Anne Russell’, for instance – try Ashwood Nurseries. Telegraph Garden shop will also deliver to your door.