Viburnum

Light and exposure

Viburnum copes with anything from full sun to partial shade, which makes it a real all-rounder. Winter-flowering species such as laurustinus or the Bodnant viburnum do best in a sheltered spot near the house, where you can enjoy their flowers and scent on the coldest days. Native species like the guelder rose take an exposed hedge line in their stride.

In partial shade, under a tree or against a north-facing wall, most viburnums keep a good shape, even if flowering is sometimes a touch less generous than in full sun. That is a real asset in gardens around Herve, which are often shaded by surrounding hedges and orchards.

Watering

Once established, viburnum is happy with ordinary Belgian rainfall and needs almost no extra watering. The first year after planting is the sensitive period: water regularly, especially through a dry spring or summer, until the roots have properly settled into the soil.

In a pot, keep a closer eye on the compost, which dries out faster than open ground. A thorough watering once or twice a week in summer is usually enough, as long as you never let water sit in the saucer.

Soil and repotting

Viburnum is not fussy about soil type. It grows equally well in acid or chalky ground, which explains why you find it in such different settings, from the hedgerows of Herve to the chalky soils further south. It does, however, prefer soil that stays moist and drains well, with plenty of organic matter.

Mulching around the base with dead leaves or well-rotted compost helps keep the soil cool in summer and cuts down on competition from weeds, particularly useful in the first year after planting.

Temperature and humidity

This is a thoroughly hardy shrub in Belgium, able to shrug off the winters around Herve, including fairly sharp frosts, without any damage. No special protection is needed, even for young plants once the first season is behind them.

Winter-flowering species such as the Bodnant viburnum sometimes flower in the middle of a freeze, and the flowers cope remarkably well with cold, simply pausing on the harshest days and picking back up as soon as the temperature lifts a little.

Pruning and upkeep

The golden rule is simple: always prune after flowering, never before. For winter or early flowering viburnums, such as laurustinus or the Bodnant viburnum, a light shaping prune is done in spring, once the last flowers have faded. For the snowball bush and other spring-flowering species, wait until late spring or early summer.

In practice, viburnum needs very little pruning to perform well. Removing dead wood, badly placed branches and lightly opening up the centre of the shrub every two or three years is enough. Overly hard pruning removes the very wood that would carry next season’s flowers.

Pests and diseases

The main pest on viburnum in our gardens is the viburnum beetle (Pyrrhalta viburni), a small beetle whose larvae riddle the leaves with holes in spring, reducing them to bare veins in the worst cases. It targets guelder rose and laurustinus above all.

The damage is mostly cosmetic and rarely fatal to the shrub. You can pick off the worst affected leaves early on, or cut out egg-bearing shoots in winter, visible as small bumps on young growth. Powdery mildew, a white felting on the leaves, sometimes appears in warm, still weather, but is not serious if the shrub gets enough air.

Propagation

Semi-ripe cuttings are the most reliable method for the home garden. In summer, take shoots from the current year’s growth that are still a little flexible at the base but already firm, cut lengths of ten to fifteen centimetres and set them in a mix of compost and sand, kept shaded and cool. Rooting takes several weeks.

Layering also works very well on an established viburnum: bend a low, supple branch down to the ground, cover part of it with soil while leaving the tip exposed, and wait for it to root before separating it from the parent plant, usually after one season.

Month-by-month care calendar

Green Hub tips

• Pick your species according to the flowering season you want to fill: Bodnant viburnum and laurustinus for winter, guelder rose and snowball bush for spring. Mix the two and you can have viburnum in flower almost all year.
• Never prune a winter or spring flowering viburnum in late summer or autumn, you would cut off the buds already formed for next season.
• If leaves get peppered with small holes in spring, think viburnum beetle rather than disease. The damage is mostly cosmetic and the shrub recovers without treatment.
• Plant a guelder rose near the vegetable patch or orchard: its flowers draw in pollinating insects and its autumn berries feed birds that, in return, clear the garden of plenty of unwanted insects.