Viburnum

Viburnums are related to the honeysuckles, so it should come as no surprise that many of them have fragrant flowers. But that's not all they have in their favour. No, this genus includes plants for all seasons and all reasons; foliage, flower, autumn colour, scent, groundcover, shrub or small tree, evergreen or deciduous, it's all there among the 120-odd species and the many hybrids and cultivars. Indeed, they're so variable that it would be quite possible to have an interesting garden of viburnums alone.

Although viburnums can be found over much of the temperate northern hemisphere and even South America, most of the common plants in our gardens, with the exceptions of the Laurustinus (Viburnum tinus) and the Guelder Rose (Viburnum opulus), occur naturally in temperate Asia or are derived from the species of that area.

About the only drawback with viburnums is that because they are so adaptable and easy to grow, they seem to have suffered from the 'familiarity breeds contempt' syndrome that sees common plants, however attractive and useful, relegated to the lower divisions of the garden league in favour of something more 'exciting'. Well, don't fall into that trap - every garden needs at least one viburnum.

Foliage

While the obvious division in the genus is between the evergreen and deciduous types, it's not quite that clear-cut. Some of the more popular plants are hybrids between evergreen and deciduous species and are semi-evergreen. This can actually be an advantage because they retain enough foliage to not look bare over winter while also developing vivid autumn tones in the leaves that fall. The very popular Viburnum × burkwoodii is the best example of this behaviour.

The foliage varies, but is in most cases a pointed elliptical shape and deeply veined. Some of the deciduous species, such as Viburnum opulus and Viburnum dentata, have lobed, somewhat maple-leaf-like foliage. Variegated foliage is not common, but where it does occur, the patterns and colours can be striking. The variegated form of Viburnum tinus is very popular.

Flowers

Viburnum flowers are nearly always white or pale pink, but within that limited colour range is found a huge variety of blooms. Although the individual flowers are small, they're massed in heads that in some types are very large indeed. Most often the flowers are all fertile, but some species have hydrangea-like flower heads in which small clusters of fertile flowers are surrounded by large sterile ray florets. Cultivars have been raised with flowerheads entirely composed of sterile flowers. A sterile Guelder Rose (Viburnum opulus 'Roseum' [syn. 'Sterile']) in full flower often droops under the weight of its huge flower heads.

Although spring is the main flowering season, many of the most fragrant viburnums start to bloom in winter, or even late autumn. Because their flowers aren't brightly coloured and insects are fewer in winter, they presumably use scent as a means to attract from a greater distance those pollinators that are around. Some, such as Viburnum × burkwoodii are rarely without a few flowers.

Fruit

In all cases, except for the sterile cultivars, the flowers are followed by berry-like drupes. While usually interestingly coloured, the drupes aren't always show, though when they are, they can be a real feature. The steel-blue fruits of Viburnum davidii are very distinctive and the black drupes of Viburnum grandiflorum are particularly large, but my favourite is the so-called High-bush Cranberry (Viburnum trilobum), which covers itself with bright red fruit in late summer and autumn. It seems that just about any plant with showy red berries gets called a cranberry, but although the fruit is edible and can be used as a substitute for cranberry, it isn't the real thing. For the record, the real cranberry, the one of jelly fame, is Vaccinium macrocarpon, a plant more closely related to rhododendrons than viburnums.

Cultivation

There isn't much to say here; viburnums are easy. Except for all but a few in the very coldest of New Zealand gardens, hardiness isn't a problem; they're not fussy about soil type; most will grow perfectly well in sun or part shade and some will grow in very dark corners. Good drainage helps but they will tolerate soil that's damp for a while.

Success with viburnums is not so much a matter of getting them to grow but directing and managing the growth they make. Although viburnums are plants with an in-built resistance to formal shaping, try to establish a good framework of main branches when the plants are young or they may develop into a mass tangled twigs rather than neat bushes.

As soon as possible after flowering, thin out any congested or weak stems and shorten back the main branches. There's nothing complicated here, it's just matter of letting more light and air into the centre of the bush and directing the plant's energy into productive wood rather than spindly growth. If this is done for the first five years or so, you should have well-shaped, heavy flowering plants.

What's available

There are many viburnums out there but garden centres tend to be rather uninspired in their selection, sticking pretty much to the tried and true. However, pester your local garden centre enough and they should be able to get hold of any of the following.

Viburnum bitchiuense

Found in southern Japan and Korea, this 3m tall deciduous shrub is beautiful in its own right while also being a parent of several attractive hybrids. It has large, strongly fragrant pink flowers that fade to white. They open in spring and are followed by black drupes.

Viburnum × bodnantense (Viburnum farreri × Viburnum grandiflorum)

A hybrid between two Chinese deciduous species, this 2.5m tall bush has rounded bright green leaves and small clusters of white flowers with a faint pink tint. The flowers are very fragrant and appear from late winter to early spring, very fragrant.

Viburnum × burkwoodii (Viburnum carlesii × Viburnum utile)

Viburnum carlesii is deciduous and Viburnum utile is evergreen, so in the spirit of compromise, their 3m tall offspring is semi-evergreen. Its rounded, bright green leaves have greyish undersides and in autumn those that fall develop intense yellow, orange and red tones before dropping. In mild areas the flowers open from late winter, elsewhere they appear in spring. They are white, opening from pink buds and are carried in ball-shaped clusters in spring. Their fragrance can scent the entirety of a small garden. Several cultivars are grown, of which the compact 'Anne Russell' is probably the most popular.

Viburnum × carlcephalum (Viburnum carlesii × Viburnum macrocephalum forma keteleeri)

Sometimes called the Korean Spice Viburnum, this deciduous hybrid grows to around 2.5m tall and its flowers really do have a spicy fragrance. They open in spring, the first blooms being pink while the later flowers tend towards white-flushed-pink. The flower heads are up to 15cm across and complement the large, rather glossy leaves.

Viburnum carlesii

At first sight this native of Korea and Japan resembles the more common Viburnum × burkwoodii, which is not surprising as it one of that hybrid's parents. However, it is fully deciduous and a more compact plant, rarely exceeding 1.8m tall. Its flowers, in ball-shaped clusters, pink in bud opening to white in spring, are very fragrant. There are quite a few cultivars of which 'Aurora' (flowers in various shades of red pink and white) and 'Cayuga' (orange autumn foliage) are the most popular. Others, such as the widely grown 'Chesapeake' are hybrids with Viburnum utile.

Viburnum davidii

While capable of growing to 1.5m tall, this western Chinese evergreen species is more commonly seen as a mounding groundcover. It has bright mid green, glossy, heavily veined leathery leaves up to 15cm long that overlap to form a dense foliage cover. Small clusters of white flowers open from late winter to mid-spring and are followed by steel blue drupes.

Viburnum dentatum

Known as Arrowwood because of its use for that purpose by native Americans, this large deciduous shrub or small tree has rather unexciting greenish white flowers and is often rather an untidy grower. However, this eastern North American species comes into its own in autumn as the black drupes ripen and the foliage develops vivid red tones.

Viburnum erubescens

This early summer-flowering, deciduous or semi-evergreen shrub is native to the Himalayas and found in mountainous areas as far south as Sri Lanka. The flowers are white flushed with pale pink and are followed by red fruits that blacken when ripe.

Viburnum farreri

Although less common than the hybrids raised from it, this 3m tall, northern Chinese, deciduous species is well worth growing for its very fragrant pink-tinted white flowers that open from mid-winter. If pollinated the flowers develop into red fruit that blackens when ripe.

Viburnum japonica

Like V. davidii, this evergreen shrub is most often seen used as a large-scale groundcover, though it's capable of growing well over 1m tall. A native of Japan, it has deep green, glossy leaves and bronze new growth. Loose clusters of white flowers in late spring are followed by red drupes. Regular trimming after flowering will keep it compact.

Viburnum lantana

The Wayfaring Tree, a species widespread in Eurasia, is a deciduous, sometimes tree-like shrub with heads of rather dull creamy-white flowers in spring. It is grown more for its fruit, which is red ageing to black, and its foliage. The leaves are attractive at all stages, starting out deep green and velvety, aging to dark green fine hairs coating their undersides, then developing gold and russet tones in autumn before falling.

Viburnum opulus

Found from Europe and North Africa to Central Asia, the Guelder Rose is a large deciduous shrub with mid green, deeply lobed, maple-like leaves that redden in autumn. Rounded heads of white flowers in spring are followed in late summer by red fruit. The bark contains a glucoside, viburnine, that has uses in herbal medicine, particularly in the control of spasms and cramps. 'Roseum' (syn. 'Sterile') is a cultivar with large heads of all-sterile flowers. It is known as the snowball tree because of the size and colour of its flowerheads and is far more widely grown than the species.

Viburnum plicatum

From China and Japan, this deciduous shrub grows to around 3m tall and has rounded, mid green, hazel-like leaves with serrated edges. Flattened clusters of white flowers in open in spring and may be followed by red fruit that blackens when ripe. The tiered branches are tiered make this species very distinctive and are a feature that is particularly apparent in the cultivar 'Mariesii'. 'Rosacea' is a cultivar with bronze young foliage and pink-tinted, all-sterile flowers in large heads.

Viburnum rhytidophyllum

While this late spring- and summer-flowering Chinese species has reasonably attractive heads of creamy-white blooms, it's really a foliage plant. The leaves are up to 20cm long and very heavily textured. The upper surfaces are slightly glossy and the undersurfaces are heavily coated in a grey to tan felt. 'Variegatum' is a cultivar with gold-splashed foliage. If the flowers interest you, look for 'Roseum', which has pinkish red blooms.

Viburnum tinus

Once one of the most popular hedging plants, though not so common now, the Laurustinus is a 3m tall, evergreen shrub from southern Europe and North Africa. It has leathery, bark olive green and in late winter and spring puts on a good display white flowers that often develop pink tints. Variegated foliage cultivars often have brighter pink flowers.

Viburnum trilobum

As described earlier, the High-bush Cranberry is a 2.5m tall, deciduous North American shrub. It has lobed, maple-like leaves that often turn bright red in autumn. Flat heads of white flowers open in spring and large clusters of very bright red berries in late summer to autumn. It is one of the best hardy shrubs for colour and quantity of fruit.

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A little searching, especially through mail order catalogues, will yield quite a few more species, hybrids and cultivars. Or you could try propagating your own. The species may be raised from seed, which is usually best stratified, but hybrids and cultivars must be propagated vegetatively, most commonly by semi-ripe cuttings.

I am a garden book author and horticultural photographer based in Christchurch, New Zealand. I run a stock photo library called Country, Farm and Garden (http://www.cfgphoto.com). This article may be re-published provided this information is published with it and is clearly visible.