Viburnum is a shrub or tree that belongs to the Adoxaceae family that is native to parts of Eurasia and North America. There are more than 150 viburnum species, most of which have ornamental foliage as well as lovely mostly white clusters of flowers and pretty blue-black fruits. Even though not all viburnums produce edible berries, they attract birds and other types of wildlife to the garden.
The various types and species of viburnum require very little pruning. But if you want to shape your shrub or promote healthy growth, it’s a good idea to prune your viburnums. The best time to prune them is generally late in winter or early spring.
When to Prune Viburnum
First of all, you need to know why you need to prune your viburnums. Reasons for pruning viburnums include shaping plants and helping to make them look more attractive as well as encouraging them to flower during the growing season.
Some gardeners don’t even bother although they will often snip them lightly in spring to encourage the formation of flower buds and flower heads. It is, though, always a good idea to remove dead flower heads and damaged branches.
If your viburnum spreads a lot and gets very leggy, that’s a good reason to prune it. At the very least, cut off any damaged branches and remove them.
The biggest challenge for amateur gardeners is that there are so many different types of viburnum and they all have slightly different needs. Let’s look at some of the most popular types.
Japanese Snowball Bush
Native to Japan and China, the Japanese snowball bush (Viburnum plicatum) grows 10-15 feet tall and just as wide. It is hardy in the USDA zones 5-8 and flowers profusely in spring.
In early- to mid-summer, when the bush stops flowering, you can remove dead and damaged branches and, if need be, shape it.
It’s important not to prune in the early spring as you will remove any flower buds that developed on last summer’s growth, which will reduce the number of buds on your shrub.
Sweet viburnum (Viburnum odoratissimum – which means it has a sweet smell!) is happiest in USDA plant hardiness zones 8-10. So, it prefers hotter conditions than the Japanese snowball bush.
V. odoratissimum will grow up to 25-30 feet tall and just as wide when it’s finished growing. After it has flowered, it gets small red berries that turn black when they are ripe.
Sweet viburnum grows quickly in the right conditions and it doesn’t need much maintenance. It is also known to be pest-free.
If you are growing this tree-type viburnum, you will need to prune it to control its size and shape. Wait until it’s stopped flowering and the berries are done, then prune it.
Blackhaw or Black Haw viburnum (Viburnum prunifolium) thrives in USDA plant hardiness zones 3-9. It is slow-growing but can grow as tall as 20-30 feet tall and 8-12 feet wide.
You can grow it as a shrub, a tree, or prune a row of them to create a hedge. It flowers in spring and should be pruned once it has stopped flowering.
David viburnum (Viburnum davidii) is a smaller shrub that grows only 3-5 feet tall and sometimes even wider, to 4-5 feet. It flowers in the fall and can also be planted as a natural screen or hedge.
Awarded the Royal Horticultural Society (RHS) Ward of Garden Merit, it produces a profusion of gorgeous flower heads with small white flowers from early spring to summer. Once the flowers die off, it gets non-edible blue berry-like fruits that add visual appeal to the plant.
This particular viburnum needs very little pruning unless you want to trim back overgrown bits. If you do prune it, it’s best to do so after it’s finished flowering.
That said, this is one of the viburnums that can be hard pruned almost to ground level if need be. But normally, a light pruning is best.
If you do decide to do a hard pruning to just a few inches from the ground, you won’t get fruit for a couple of years.
Leatherleaf viburnum (V. rhytidophyllum) is another type that grows big – up to 10-15 feet high with the same kind of spread. It works well in an informal border, which means you don’t have to do anything more than regular light pruning.
Leatherleaf viburnum can be pruned after it has flowered late in spring. Don’t wait until winter when most other shrubs are dormant because this is when their buds will have formed.
Arrowwood viburnum (V. dentatum) grows happily in USDA plant hardiness zones 3-8 and will reach anything from 6-15 feet in height. It will also end up as wide as it is tall.
Prune in spring after the shrub has flowered. If any of the stems are leggy or old and woody, cut them to ground level.
V. dentatum, like most other types, only needs light pruning. The idea is to trim the shrub to maintain its shape and to remove any dead or damaged branches.
You don’t want to trim too much, or you will remove the developing fruit.
Sandankwa viburnum (V. suspensum) can grow to a height of anything between 6 and 12 feet. It thrives in USDA plant hardiness zones 8-11.
The best time to prune Sandankwa viburnum is directly after it has flowered in spring. You can prune it to near ground level to encourage rejuvenation.
It’s best not to shear it to create a formal hedge because it has larger leaves than other viburnums.
Viburnum Snowball Bush
The snowball viburnum bush (Viburnum x carlcephalum) produces pretty, rounded flower heads that look a bit like snowballs. They grow up to about 20 feet tall and generally bloom in spring.
Unlike most viburnums, they don’t produce berries after they have flowered. So, the best time to prune them is as soon as they have stopped flowering.
The snowball viburnum doesn’t need heavy or regular pruning. You can cut it back every couple of years just to control its size and maintain its shape.
Korean Spice Viburnum
Korean spice viburnum (Viburnum carlesii) has leaves that are similar to the lovely snowball bush, turning a burgundy-purple color in the fall. But it’s a lot smaller in size and only grows to about 4-8 feet when mature.
If you’re going to prune your Korean spic viburnum bushes, the University of Illinois Extension advises you to pay careful attention to timing.
They warn that if you aim to improve the performance of your spring-flowering, Korean spice viburnum shrubs in Illinois, you should prune when they are dormant. But, there is a caveat.
Many woody shrubs are dormant in winter and even in early spring. But, because Korean spice viburnums flower in spring, if you prune them in winter you are likely to remove many, if not all, of the newly sprouted flower buds.
So, rather than rely on the seasons, wait until your bushes have flowered, and then prune them.
Mapleleaf viburnum (V. acerifolium) is a prolific plant that is common in the eastern regions of North America. Its distinctively shaped leaves, which resemble those of maple trees, provide food for wild animals in forests, on undeveloped hillsides, and next to rivers and lakes.
V. acerifolium is a popular plant in landscaped native gardens in this part of the world. Although often smaller in their natural environment, these shrubs can grow as tall as 6 feet and up to 4 feet wide.
This is one type of viburnum that isn’t improved visually by pruning. If you want to control its size, prune in late winter to early spring before it flowers in the growing season.
Viburnum Awabuki ‘Chindo’
Chindo viburnum (V. awabuki Chindo) grows in the temperate USDA plant hardiness zones 7b-9. It can grow as tall as 15 feet.
V. awabuki Chindo flowers in spring and early summer. It doesn’t need more than light pruning to remove damaged branches and dead flower heads.
The caveat here is that you will lose some if not all of the berries that birds love so much. The alternative is to prune lightly the following spring, after the last hard frost.
You may have fewer flowers, but you and the birds will get to enjoy the pretty berries over the winter of the previous year.
Laurustinus viburnum (V. tinus) is native to the Mediterranean regions and flourishes in USDA zone 8 and warmer. There are various Laurustine shrubs. Depending on the type, they will grow to heights of anything from 6-12 feet.
There is no real reason to prune Laurustine shrubs except to reshape the shrub and maintain a smaller size. Pruning it every 2 or 3 years will encourage it to flower.
How to Prune Viburnum
Whichever viburnum species you prune, be prepared for the job. Long sleeves, long pants, and shoes will protect your arms, legs, and feet from getting scratched by branches.
The way you prune will depend on your motivation. So, ask yourself why you are pruning your viburnums.
Do you want to encourage flowering or do you want to shape your bushes? Are you planning to prune as a pest-control method?
Here’s a good, general method for annual pruning of most types:
Remove Damaged Branches
If any branches are damaged or are dying, cut them off. Do this with clean, sharp secateurs and cut to a leaf node or bud.
Get Rid of Clip Suckers & New Stems
If you want to keep the shrub from spreading, clip all new stems and suckers at the base of the plant as soon as they appear.
Prune Stems Once They Have Flowered
After the plant has flowered, cut it back. You want to do this as soon as possible so that buds don’t start to form. If they do, this will reduce the flowers for the following year.
Shape Your Plants
A good way to promote new growth and shape your viburnums is to remove the oldest stems close to the base of the shrubs. This opens up the plant and allows air to circulate and light to penetrate.
Apart from anything else, it’s not going to flower on old wood.
When to Hard Prune
You’ll soon get the idea of when to hard prune viburnum. Just be sure not to remove more than a third of the branches or you can create stress that can kill the plant.
You can cut a few species to ground level. But it isn’t usually necessary unless you haven’t trimmed it regularly. It will depend on the growth habit of each plant.
There are different ways to prune viburnums.
Tip 1: Ways to prune viburnums
If you pinch the stem tips of young plants you will promote branching and avoid the need for hard pruning later.
Thinning will improve air circulation and will allow more light into the bush. Do this by removing old wood back to the trunk.
If you plant viburnums to form a hedge, you will need to level the surfaces of the shrubs by shearing them. This is how you keep the shape of the hedge.
Tip 2: Water well after pruning
After you’ve pruned your viburnum it’s a good idea to water it well to counter the stress. Lots of water will also encourage root growth.
Tip 3: Wear rubber gloves
Safety glasses will protect your eyes and gloves will protect your hands. Nitrile gloves, made from synthetic rubber, provide added protection.
Tip 4: Use the right tool for the job
Use anvil pruners if branches are less than ⅝-inch in diameter and loppers if they are up to 2½ inches thick.
Viburnums are low-maintenance shrubs and trees, many of which make great formal or informal hedges. Light pruning is generally all that is needed.
A good rule of thumb is to prune your viburnums soon after they have flowered.