Care of a Snowball Bush

The snowball bush (Viburnum spp.) adds showy flowers and lovely fall color to your outdoor space without requiring too much care and maintenance. Some common species include the European snowball bush (Viburnum opulus 'Roseum'), which grows perennially in U.S. Department of Agriculture plant hardiness zones 3 to 8; Chinese snowball bush (Viburnum macrocephalum), which is hardy in USDA zones 7 to 9; and Japanese snowball bush (Viburnum plicatum), which is hardy in USDA zones 5 to 8. Choose a planting spot with enough room for the plant’s mature size and the plant nearly cares for itself.

Snowball bushes grow well in areas with full sun to partial shade. Space plants at least 5 feet apart, although species such as Japanese snowballs, which grow 8 to 10 feet tall and wider than they are tall -- need as much as 15 feet of space. Plan your planting bed for the snowball bush's projected mature size to avoid having to move the shrub or do any heavy pruning.

Choose a planting area with well-drained soil. Before planting a snowball bush, till the planting area to help aerate the soil and break up any clumps. Till a 2- to 3-inch layer of compost into the top 9 inches of soil to enrich the planting area. If you have heavy soil that doesn't drain well, spread a 4-inch layer of sand over the planting area and till it into the top 9 inches of soil to improve drainage. Add a 2- to 3-inch layer of hardwood mulch to the planting area to conserve soil moisture and keep the area weed-free.

Water the snowball bush as needed to maintain even moisture after planting it, and then only when your area receives less than 1 inch of rain per week during the heat of the summer. Avoid watering the plant overhead; instead, water it deeply at ground level. Concentrate on watering it around the perimeter of the bush's outermost foliage -- also known at the drip line. Continue watering the snowball bush until the top 12 inches of soil are moist.

Fertilize your snowball bush annually each spring, before the plant shows signs of new growth. Use a balanced, slow-release formula such as a 14-14-14 blend. Apply approximately 1/4 cup of fertilizer for each cubic foot of planting area, or according to package directions. Water the area thoroughly after applying fertilizer.

Snowball bushes are generally self-maintaining, so you don't really need to worry much about pruning. Fine Gardening recommends inspecting your shrub periodically to remove any limbs that are dead, damaged or show signs of disease -- a practice that can be done at any time of year.

If your snowball bush is so overgrown that it's flopping over, perform drastic rejuvenation pruning by cutting it back to 1 foot tall in late winter. A gentler approach is to prune approximately 30 percent of the plant's older growth every year for three years.

Disinfect your pruning tools, especially if you're trimming diseased branches, by spraying them with household disinfecting spray and allowing the tools to air dry before continuing to prune plants.

In general, pests don’t affect snowball bushes, but two offenders occasionally cause damage.

Snowball aphids lay their eggs on or near viburnum flower buds in autumn and the eggs hatch in spring once the flowers begin to bloom. These small, gray insects feed on the plant's new growth, causing the foliage to become twisted and distorted. Control these aphids by spraying the tops and undersides of the foliage and flowers of affected plants with ready-to-use insecticidal soap and prune any damaged limbs from the plant.

Another pest to keep an eye out for is the viburnum leaf beetle, a small gray-brown pest that causes defoliation of the shrubs. If you notice any buds that fail to expand, there may be viburnum beetle eggs waiting to hatch. Control these pests by pruning any egg-infested limbs before they hatch in mid-spring or remove the adult beetles and larvae by hand. Alternatively, treat affected plants by evenly spraying the foliage with an insecticide that contains spinosad, a natural insect killer that doesn't typically harm beneficial insects. Combine roughly 4 tablespoons of the insecticide for each gallon of water and spray the mixture onto the foliage using a trigger sprayer or a hose-end sprayer.

Snowball bushes rarely fall victim to diseases as long as they have plenty of air circulation. If these versatile shrubs are overcrowded, however, they may develop fungal diseases such as leaf spot, which generally causes discolored spots on the foliage. Other common problems include powdery and downy mildews, both of which cause fuzzy gray fungal growth on the leaves. In addition to planting snowball bushes with adequate spacing, keeping the foliage as dry as possible helps to prevent these fungal problems.

If necessary, spray the tops and underside of the foliage of infected plants with a ready-mixed fungicide labelled for the specific problem. For example, a fungicide that contains chlorothalonil treats fungal leaf spots and downy mildew, while formulas made with myclobutanil or propiconazole treat powdery mildew.