How to grow Viburnum
Viburnum is an extremely varied genus of shrubs. Depending on the species (there are more than 150), viburnum may be deciduous or evergreen, large or small, and winter or spring flowering. There is no single type of flower: some bear round, pom-pom-like heads, while others (typically the winter-flowering types) have small clusters of tubular blooms. There are also those which produce flattened sprays more like lacecap hydrangeas – the two looking so similar it’s hard to believe they’re not related. Often, flowers are followed by attractive berries. Some deciduous species also offer good autumn colour, while evergreen types make effective hedges and screens.
Although hugely diverse, all viburnums share in common a robust, easy, fuss-free nature. Most are best left to their own devices, though respond well to a rejuvenating hard prune if needed. Whether a sunny, open spot or deep shade, a viburnum can be found to suit most situations.
Zantedeschia is a genus of flowering plants from the family Araceae and is native to southern Africa. With a rich history dating back to the Ancient Romans, these deciduous or semi-evergreen perennials have been used as a symbol of celebration. Zantedeschia was Named after Professor Giovanni Zantedeschia, an Italian botanist.
There are two main forms of Zantedeschia: hardy and tender. Hardy forms of the plant can be grown outdoors, enjoy moist soil and full sun or partially shaded conditions - these are known as Arum lilies. Tender forms of Zantedeschia prefer being grown in containers or pots and should be brought inside over the winter - these are known as Calla lilies.
With tuberous flora in all colours from whites, yellows and oranges to deep reds and purples, Zantedeschias are not to be overlooked in any garden, as long as they have sufficient sunlight to grow in.
Ready to learn more about growing Zantedeschia? Read on for all there is to know...
Key Information
Soil pH
Position
Hardiness
Key Information
Position - Most prefer a sunny, open spot or partial shade. Others tolerate full shade, particularly Viburnum tinus.
Soil - Will grow in almost any reasonable soil. V. opulus will also tolerate wet, heavy soil.
Flowering Period - Mostly spring flowering, with a handful of species flowering in winter.
Hardiness - Hardy, ranging from H4 (-5 to -10°C, i.e., an average UK winter), to H7 (-20°C and beyond).
Horticultural Divisions
While there are many different species and cultivars, here are a selection of those we currently stock.
Deciduous spring-flowering viburnum
Viburnum opulus ‘Roseum’ A popular, cultivated form of our native species known as the guelder rose. Rather than the flattened, lacecap-like flowerheads of the straight species, ‘Roseum’ produces rounded, pom-pom-like blooms, leading to a common name of snowball tree. Leaves become purple-tinted in autumn. This is a sterile form, so does not produce the red berries of its parent. Particularly good at thriving in wet conditions.
V. plicatum A lacecap-type flowering species from China and Japan. Blooms are usually abundant in spring, though some forms (‘Watanabe’) continue flowering into autumn. Good autumn colour.
Deciduous winter-flowering viburnum
V. x bodnantense ‘Dawn’ Bears small clusters of highly scented, dark pink flowers on bare stems over a long period from late autumn to spring. Popular winter-interest plant. A sterile hybrid, meaning little or no berries.
V. x bodnantense ‘Charles Lamont’ Similar to ‘Dawn’, though with brighter pink flowers.
V.farreri A parent of the x bodnantense hybrid, with smaller, paler flowers, mainly in late autumn though will continue through winter and into spring in mild weather. Bright red berries follow. Native to China. Several, compact cultivars offer a smaller, more manageable alternative to the x bodnantense hybrids, which can become quite tall and rangy. ‘Candidissimum’ and ‘December Dwarf’ are two of our favourites.
Evergreen viburnum
Although easy to grow, evergreen viburnum tend to be slightly less hardy than deciduous species (they have to brave winter head on, rather than waiting it out in dormant mode!). It’s best, therefore, to avoid planting in a very cold, exposed spot, particularly if you’re further north.
V. tinus A useful, almost ‘bombproof’ Mediterranean shrub that will grow in a range of difficult conditions, including deep shade, very dry soil, and salty sea winds. Produces flattened, white flowerheads from late winter to spring. Popular cultivars include ‘Eve Price’, with shorter leaves and pink flower buds, and ‘Gwenllian’, which bears an abundance of pink-flushed white flowers from dark pink buds. Dark, metallic-blue fruits follow.
V. odoratissimum ‘Coppertop’ An increasingly popular new form of this glossy, evergreen species, remaining more compact and producing glowing bronze new foliage. A fresh alternative to Photinia ‘Red Robin’.
Where and when to plant Viburnum
Deciduous species can be planted anytime during dormancy, i.e., the period from autumn to early spring (avoiding days when the ground is frozen).
Evergreens are best planted in either autumn or early spring. An autumn planting can be done by those gardening in mild conditions (and broadly speaking, this is the southern half of the UK). For those liable to cold, wet winters, it is best to wait until spring (generally the northern half of the UK, or those with very heavy soil). It’s best to avoid a summer planting, as woody plants struggle to establish well from this. If you acquire your viburnum outside of the optimum planting window, we recommend potting into a slightly larger container and growing on until the time is right.
Viburnums can be left to grow naturally as attractive, free-standing specimens, perhaps in a shrub border or as understory planting beneath trees. They also respond well to clipping and can be grown as hedging. Plant winter-flowering species where their scent and beauty will be encountered regularly during the colder months, such as near a doorway or much-used path. Remember that these are much less spectacular during summer and autumn, so are best grown amongst other plants which can take over as the growing season progresses.
Like most woody plants, viburnum prefers life in the open ground though can be grown in a container if necessary. Compact and dwarf forms are best for this. Expect a much smaller eventual size than when grown in the ground.
How to plant Viburnum
Water well and allow to drain before planting. Then:
· For planting in the open ground, dig the soil area over, removing any large stones and weeds and breaking up any lumps. Mix in plenty of organic matter such as manure or garden compost.
· Rake level and firm with your heels. Rake level again.
· Dig a hole twice the width of the roots.
· Place the plant in the hole, ensuring the top of the root ball sits level with the surface of the soil. Too high and the roots can dry out, too low and the stem can rot.
· Backfill with soil and firm in gently with your foot.
· Soak well with water.
· Mulch around the base with well-rotted organic matter such as manure or garden compost.
- For planting in a container, first choose an appropriately sized pot. The best practice is to start just a few centimetres larger than the rootball and repot into a slightly larger size every year. Always ensure there are plenty of drainage holes in the bottom.
- If you are using a large or heavy pot, it can be a good idea to fill and plant it in situ to save yourself the trouble of moving once full.
- Use a loam-based compost suitable for mature plants (John Innes No 3 is ideal), with a little horticultural grit mixed in, and, if not already present in the compost (check the description on the bag) some slow-release fertiliser granules.
- Start by partially filling the pot with compost; enough so that when placed on it the top of the roots sits about 3 centimetres lower than the top of the pot.
- Infill all the space surrounding the roots with compost, firming down with your fingers then adding a little more so the plant is held tight.
- Pick up the pot (if you can!) and lightly tap on the potting bench or ground a few times to help further settle the compost around the plant.
- Soak well with water.
- A mulch with horticultural grit will look attractive and help to prevent a ‘cap’ or crust forming on the top of the compost (something container plants can suffer due to the artificial nature of their watering).
What to plant with Viburnum
Winter-flowering species fit naturally with other plants that are also at their most interesting during the cooler months. For similarly bare-stemmed beauties think callicarpa, hamamelis, chimonanthus, and edgeworthia. Add a smattering of snowdrops and hellebores at their feet to complete the winter wonderland.
Spring-flowering viburnum can look spectacular when relating to the blossom of a nearby flowering cherry, amelanchier, or magnolia. To extend the interest, grow amongst a few later flowering shrubs such as weigela, philadelphus, and hydrangea.
How to care for Viburnum
Pruning and Deadheading
When grown as a freestanding shrub, viburnum requires little pruning and is in fact best left to its own devices apart from the occasional removal of dead, diseased, or damaged wood. This is best done immediately after flowering.
Viburnum grown as a hedge can be trimmed each year in autumn. Try to avoid cutting hedges between March and September, as this risks disturbing nesting birds.
Most deciduous species, along with the evergreen V. tinus, respond well to a hard prune, which can be needed if they have outgrown a space or are looking tired and neglected. This is best staggered over three years, cutting out a third of the oldest wood at the base each year. Do this in late winter for deciduous types, early spring for evergreens.
Watering
Like all woody plants, viburnum should be regularly watered during its first couple of growing seasons in the ground while its roots become established. After this, the watering requirements vary. Deciduous species tend to be more shallow rooting (especially summer-flowering ones) and will benefit from being watered during prolonged periods of hot, dry weather. Evergreen species are more drought tolerant and rarely require watering once established.
Container-grown viburnum has less access to moisture so will need to be regularly watered throughout every growing season. A useful rule of thumb to avoid overdoing it is to only water once the top couple of centimetres of compost have dried out. Be aware, however, that during the height of summer this can happen in as little as 24 hours. From mid-autumn, the British climate tends to take over watering needs, though do remember to step in in the event of an unseasonably dry spell.
Feeding
To give it the best possible start, feed viburnum for its first couple of years in the ground with a general-purpose granular feed or blood, fish and bone, applied to the surface of the soil and lightly worked in (known as a ‘top dress’). This is best done in late winter, along with a mulch of well-rotted organic matter. By this we mean a layer of manure or garden compost applied to the soil around the plant, which, as well as improving the soil structure and nutrient content, also suppresses weeds and locks in moisture.
Once your viburnum is established, an annual mulch should provide sufficient nutrients, however, apply a top dress as above if ever you feel an extra boost is needed.
Container-grown plants rely more on the gardener for nutrition. Get off to a flying start by making sure you use a good quality, loam-based compost with slow-release granules mixed in, then throughout the growing season (March to September) apply a monthly liquid feed. Remember to repot into a slightly larger pot using fresh compost every couple of years. In the intervening years, and annually once this is no longer feasible, carry out a topdress in spring. Scrape away the top 5 centimetres of compost and replace with fresh, remembering to mix in a little general-purpose slow-release feed.
Cold Protection
Most viburnum species are hardy enough to withstand a UK winter without the need for additional protection. Evergreens tend to be slightly less hardy and may struggle if exposed to very low temperatures. These grow best in the milder, southern regions or tucked away out of strong, cold winds.
Pests and Diseases
Viburnum tends to be fairly robust, though if you do spot pest damage it is likely to be one of the following culprits:
- Viburnum beetle (causes defoliation, mainly found on V. tinus and V. opulus)
- Aphids (can result in distorted growth and sooty mould, mainly found on V. opulus)
- Scale insects (causes sooty mould, mainly found on V. tinus)
Small populations of these are unlikely to do major harm and should be tolerated where possible. As always, we recommend the best line of defence to be creating a healthy, balanced garden ecosystem by encouraging as many species of insects and mammals into the garden as possible. Natural predators of these pests include ladybirds, wasps, and birds, so try to boost their numbers by growing a wide range of pollinator-friendly plants, not using chemicals, and providing suitable habitats.
Honey fungus can also be a problem, though is mercifully rare unless you’re near a heavily wooded area. It can be identified by dieback and sparse foliage, and fungal fruiting bodies at the base of the shrub. Unfortunately, little can be done other than removing the affected specimen and replacing with a known resistant alternative.
How to propagate Viburnum
Viburnum may be propagated by cuttings, taken at different times of year depending on type.
Deciduous species can be propagated by hardwood cuttings taken during winter:
- Select shoots of fully ripe, current year growth, cutting at the join with last year’s growth.
- Trim to 15-20 centimetres, with the top cut just above a pair of buds, and the bottom cut just below a pair of buds. It is good practice to make the top cut sloping, both to aid water runoff, and as a reminder of which end is which.
- Spacing approximately 10-15 centimetres apart, firm into a trench in a prepared bed (with well-rotted organic matter and grit dug in), the top 3-5 centimetres of the cutting showing above soil level. Alternatively insert into containers filled with a gritty compost mix.
- Water in lightly. Place containers in a cold frame or unheated greenhouse.
- Check and re-firm trench cuttings after a frost (which can lift them out of the ground).
- Leave cuttings in place until the following autumn ensuring they do not dry out during the summer. By this point they should have rooted and can be lifted and either potted or planted out as required.
Evergreen species are better propagated by cuttings taken from late spring to early summer:
· Find non-flowered shoots 5-10 centimetres long and snip off the plant.
· Put in a plastic bag straight away to prevent drying out.
· Fill a container with a well-draining compost mix comprising at least 50% perlite or grit.
· Trim the end of the cutting to just below a pair of buds.
· Remove the lowest third of leaves.
· If the remaining leaves are large, cut them in half with a sharp knife (to reduce water lost through transpiration).
· Insert the cuttings into the compost and water lightly. Several cuttings can be put in the same container if there is enough space to do this without them touching.
· Place in a propagating unit with bottom heat if you have one or covered with a plastic bag on a windowsill or in a greenhouse if not (out of direct sunlight).
· Keep the cuttings misted and occasionally watered until they root. You will know this has happened when roots emerge out of the bottom of the container.
· Gently remove rooted cuttings and pot them into individual pots. Grow on in a cool yet frost-free environment such as an unheated conservatory, greenhouse, or cold frame, until they are large enough to be planted out.
* Many plants carry Plant Breeders Rights and cannot be propagated for commercial purposes.
Common Viburnum Questions
· Is viburnum a good garden shrub?
Viburnum has excellent garden value, offering pretty flowers, often attractive fruit, and either good autumn colour or evergreen structure. It is used as cover for many species of garden bird all while asking very little of the gardener. What we call ‘a real doer’!
· Will viburnum grow in total shade?
While most species prefer at least partial sun, we have seen V. tinus growing quite happily in a deeply shaded spot. Definitely a good one to have on the ‘plants for tricky spots’ list!
