Wandering through the garden recently on a hot, sunny morning I was drawn to one shrub because of the sound emanating from it…once I arrived I found the entire plant was covered with bees – wild honeybees, masonry bees, leaf-cutter bees and other solitary species – together with hoverflies of half-a-dozen different species. Even some pollen-eating horned-beetles had flown in to join the scrum, and there must have been getting on for a thousand individual insects all feeding together on one plant.
The shrub in question was a Viburnum dentatum, and the big draw for all the many insects were the flowers, many hundreds of which were covering the plant, each one laden with pollen. Our garden teems with wildlife at most times, but I was particularly pleased to think that just one individual plant was providing to much sustenance to so many wonderful insects and their various hungry broods back in their respective nests.
Viburnum dentatum is a North American species, and not necessarily one of the most ornamental of this strikingly handsome genus. Over in our hedgerows, though, both of the native species of Viburnum – V. lantana – aka the Wayfaring Tree – and V. opulus, the Guelder Rose – are doing their thing. The plants of Viburnum opulus that grow wild around the margins of the garden are all interwoven into the hedgerows and so get cut back pretty hard every couple of years, which certainly doesn’t do much for their flowering display, but where they do flower these too are smothered with feeding insects feasting on the bounty of pollen.
Viburnum opulus in full flower - a major insect magnet.
Viburnum opulus is one of our most attractive and versatile native shrubs. Not fussy as to soil type, the plants tolerate dry, infertile soils but particularly thrive in wet or boggy soils where, aside from huge trees, relatively few other native woody plants will succeed. Our largest pond is bordered by soil that was, at least in part, formed by the spoil from its excavation – rich but very heavy clay. The area also periodically floods from the river and is subject to continual leaching of water from the body of the pond.
We originally planted this mini-zone with a variety of selections of Acer palmatum, with their traditional association with water, but the continually wet soil has proven too much for these Maples, all of which failed to thrive and were moved to another part of the garden this last winter. This pond-margin has now been replanted with a group of different cultivars of Viburnum opulus which have already produced great growth and seem to be positively relishing their semi-boggy new homes. The future display of flowers, all interweaving from the different varieties, should prove to be an even bigger insect magnet than their American cousin Viburnum detatum over on the other side of the garden.
Viburnum opulus - the wild form.
Viburnum are closely related to Hydrangea, and the flowers of V. opulus are amongst the finest in the whole genus, closely resembling those of a Lacecap Hydrangea. The common name ‘Guelder Rose’ is one of those widespread, but not very useful or accurate labels that sometimes get attached to plants, this time stemming from the introduction of one very well known form of the species – V. opulus ‘Roseum’, widely known as the Snowball Tree. This very popular cultivar was believed to have been found in the Dutch region of Guelderland, hence the name, but, from a wildlife perspective, the Snowball tree should be avoided entirely. Those large balls of flowers are completely sterile – so no pollen is produced at all, not much good for hungry bees and hoverflies.
The flowers of Viburnum opulus 'Roseum' are big and blowsy, but not much good for hungry wildlife.
Being sterile ‘Roseum’ also fails to set fruit, which brings me to another great attribute of the species. Once the flowers have fallen away the plants produce heavy clusters of cranberry-like, glistening bright-red fruits. These are absolutely beautiful to behold, particularly on the varieties with contrasting leaf colour (more of which in a moment…) but, as might be imagined, they are also highly valuable to birds busily feeding-up for the coming winter. The Thrush family are particularly fond of these fruits, and blackbirds, mistle thrushes, fieldfares and redwings will all go out of their way to visit and feed upon a fruiting bush. Woodmice and field mice are also fans of the fruit and have been known to scale the shrubs in search of a meal.
Big clusters of fruit bring in the birds (and the mice).
From an ornamental perspective – pretty important for any large shrub if it’s is going to deserve a space in most gardens, after all – the flower and the fruit are followed by another top feature, namely autumn colour. The foliage of most varieties turns to a range of colours from deep purple-burgundy to bright crimson and orange, depending on the temperatures, and is especially vivid when the plants are grown in full sun. A plant of Viburnum opulus in full autumn colour, and at the same time laden with it’s bright fruits, is pretty hard to top when it comes to seasonal finery, and all this from a common and easily grown British native.
Viburnum opulus, in autumn foliage.
Besides the aforementioned ‘Roseum’ there are surprisingly few named forms of the species, but those that do exist are generally all well worth growing. ‘Aureum’ is an old, golden-leafed cultivar that tends to burn when grown in full sun. It’s now been superseded by the much more weather-proof ‘Park Harvest’ which, come early autumn, combines it’s intensely yellow leaves with vivid red fruit – quite a spectacle.
Viburnum opulus 'Park Harvest' - the new golden foliage lined with red.
‘Xanthocarpum’ and the newly selected ‘Apricot’ have yellow and pink-ish gold fruit respectively, whilst ‘Notcutt’s Variety’ has larger flowers and fruits. Perhaps most useful of all is ‘Compactum’, a very free-flowering and strong fruiting cultivar that forms a dense and compact shrub, ultimately much smaller than the wild form, and so more readily accommodated in smaller gardens.
Viburnum opulus 'Xanthocarpum'.
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