This bush and its berries are non-toxic, but consuming large quantities of berries can cause stomach upset in some people. They are, however, of great appeal to birds. When choosing a location, keep in mind that snowball bush viburnum will grow fairly large. Pick a spot that will provide lots of sun and allow for the mature size of the bush. Once established, the shrub will be very easy to maintain—It should be fertilized only once per year and pruning is optional. While some viburnums are considered invasive in many regions, snowball bush viburnum is not one of these. But do take care that you are growing this hybrid, and not Japanese snowball (Viburnum plicatum) a similar-looking shrub that is most definitely invasive.
Light
The best location for a snowball bush viburnum is usually in full sun, especially in the cooler northern part of its range. The snowball bush likes at least six hours of sunlight per day in order to produce the biggest masses of flowers. A location in partial shade may be better for gardeners in a location that gets consistently warmer weather.
Soil
The snowball bush prefers well-drained, loamy soil but it isn’t too particular and grows well in many different soil types. It tolerates a wide range of soil pH but prefers moderately acidic soil.
Water
Water your snowball bush enough to keep its soil evenly moist, as it does not like dry ground. A suggested schedule is 1 inch per week, but you should plan to water it more often if experiencing extreme heat. Additionally, you can conserve soil moisture by applying a thick layer of landscape mulch around your shrub, which will have the bonus effect of suppressing weeds.
Temperature and Humidity
The snowball bush can tolerate the freezing winter temperature of zone 6 and the summer heat down to zone 8, but does not do well in climates that are warmer or colder than this. It can thrive in both dry and humid conditions, provided air circulation and soil drainage is good.
Fertilizer
Fertilize your snowball bush plant in the spring with a slow-release fertilizer, or work compost into the earth around the plant at any time. Be careful not to go overboard—fertilizing too much can inhibit the plant’s blossoms, especially if it gets too much nitrogen.
Snowball Bush Viburnum Varieties
While there are several different plants that have commandeered the name “snowball bush” over the years, there are very few cultivars of the true snowball bush viburnum. There are, however, some closely related snowball-type hybrid viburnums:
Cayuga viburnum is a cross between V. carlesii (Korean spice viburnum) and V. x carlcephalum. It has a more compact growth habit (4 to 10 feet tall and wide) and blooms profusely with 4-inch white clusters in spring. Judd viburnum (Viburnum x juddii) is a cross between V. carlesii and V. bitchiunse, producing a very appealing shrub that is hardy in zones 4 to 8. It is more resistant to leaf spot infection, and propagates more easily; some experts prefer it to V. x carlcephalum.
Pruning Snowball Bush Viburnum
Prune lightly if needed (for example, if you are growing it in a tight spot) just after the flowering period is over, or if using it in hedge application. You can cut the flowers to use in floral displays—if you aren’t cutting them, pinch off the spent blossoms to encourage new growth. When necessary, this shrub will tolerate hard pruning to ground level as a means for renovating the plant.
Propagating Snowball Bush Viburnum
As with many woody shrubs, propagation of snowball bush viburnum is best accomplished through softwood cuttings. Timing is important, since the cutting will root best if the new wood is still green but just hard enough to stand on its own without flopping over. In most regions, late spring or early summer is the best time to propagate the plant. Here’s how to do it:
How to Grow Snowball Bush Viburnum From Seed
This is a hybrid shrub that will not reproduce itself accurately from its seeds. Thus, it is always propagated from softwood cuttings.
Overwintering
In zones 7 and 8 this shrub requires no special winter protection, but zone 6 gardeners may want to cover the ground area beneath the shrub with a thick layer of mulch for the winter. These are shallow-rooted plants that can be susceptible to frost; the mulch will also help preserve moisture in regions where winters are dry.
Common Pests & Plant Diseases
Like most plants, you may occasionally have to treat this shrub for disease problems or bug infestations, but preventive measures can be taken. It is a good idea to leave space between your snowball bush and other plants to reduce the chance of attack by bacterial leaf spot or powdery mildew. Aphids are also a common problem for the snowball bush—if you notice them on the leaves, spray the bush with an organic insecticide such as neem oil. Viburnums are notoriously susceptible to bacterial leaf spot diseases, which can be hard to manage once the disease becomes established. Badly affected plants usually need to be removed.
How to Get Snowball Bush Viburnum to Bloom
These shrubs need to cross-pollinate in order to bloom. If yours doesn’t bloom profusely, then it will likely help to plant one or two additional snowball bush viburnums in the area. Many landscapers plant this shrub in groups for this reason. Too much shade can also reduce flowering. Pruning nearby trees to open up sunlight can help. Another major reason for non-flowering is improper pruning. Viburnums bloom on old wood, so if a shrub is pruned too early in the spring or too late in the fall, you will eliminate the potential for spring blooms. Always prune this shrub immediately after it has flowered. This gives the shrub plenty of time to develop the wood that will provide next year’s flowers. A viburnum that is getting a lot of nitrogen fertilizer, such as runoff from lawn feeding, can experience reduced flowering, since the nitrogen fuels foliage growth at the expense of flowers. Changing the feeding routine to a product with more phosphate can help.
Common Problems With Snowball Bush Viburnum
The reason for the vast popularity of viburnums is that they are such easy-to-grow plants. But here are some things to watch for with snowball bush viburnum.
Stem Die Back to Ground Level
This is a symptom of the viburnum crown borer. These wood-boring insects penetrate the stems near ground level, causing the stem to die back. Untreated, these pests can kill the entire plant. Healthy, undamaged plants are much less likely to succumb to this pest. Once affected, beneficial nematodes (Heterohabditis bacteriophora) applied as soil drench can kill the insects. Chemical pesticides sprayed early in the season on the lower bark can prevent the insect from gaining a foothold.
White Powder on Leaves
This is a symptom of powdery mildew, an unattractive but rarely fatal fungal disease. Giving the shrubs plenty of air circulation and watering them at ground level rather than overhead can help prevent the disease from gaining a foothold. Remove diseased leaves as they appear, and make sure not to add this material to compost heaps. Clean up and discard the debris around the plant at the end of the season to prevent the spores from overwintering and reinfecting the plants in the spring. Chemical fungicides are sometimes effective if you spray when the fungus first appears. But powdery mildew often appears fairly late in the season, and many gardeners don’t bother to treat it at all.
Leaf Spots
Random spots on the leaves of viburnum are usually evidence of a bacterial infection. Where such diseases are present, carefully remove affected plant parts and make sure to sterilize cutting tools between each pruning cut. There is no effective cure for bacterial diseases, other than isolation, so badly affected plants should be removed.
