All snowball bushes (Viburnum spp.) root effortlessly from cuttings, although the type of cutting that works best varies slightly among species. The resulting snowball bushes will be identical to the parent plant with the same globular, snow-white flower clusters.
Snowball Bush Types
Several shrubs share the common name snowball bush, including the European snowball viburnum (Viburnum opulus 'Roseum'), Chinese snowball viburnum (Viburnum macrocephalum) and Japanese snowball bush (Viburnum plicatum f. plicatum 'Popcorn').
Hardiness varies among species. The European snowball viburnum grows in U.S. Department of Agriculture plant hardiness zones 4 through 8, while Chinese snowball viburnum performs best in USDA zones 6 through 9. Japanese snowball bush grows in USDA zones 5 through 8.
Viburnums root best from softwood cuttings taken in late spring before flowers form, although European snowball bush will also root from hardwood cuttings taken in winter from the previous seasons' growth. A 4- to 6-inch cutting taken from the tip of a branch works best, but it must be leafy and free of buds and flowers. When choosing cuttings, make sure they have multiple leaf nodes along their stem, and that:
- Hardwood cuttings are about as thick as a pencil and have brown, hardened bark.
- Softwood cuttings have greenish bark and a bendable stem.
Before taking cuttings, soak the blade of a sharp, non-serrated knife in a solution of 1 part bleach and 3 parts water for at least five minutes to kill off any harmful bacteria. Rinse the blade in fresh hot water and let it air dry before using it.
Warmth and humidity play a vital role in rooting snowball bush cuttings, but perhaps the most important factor is speed. Pot up the cuttings as soon as possible after gathering them, and wrap them in moist paper towel while preparing their rooting containers. Or, have the containers ready before you go to take the cuttings.
Fill a 1-gallon plastic pot with moist, sterile medium such as a mix of half perlite and half peat. Choose a pot with drainage holes and wash it thoroughly before use.
Remove the leaves from the bottom one-third of the snowball bush cutting. Also, remove half of the leaves from the tip to limit moisture loss. Remove any buds or flowers, as well.
Measure out a rounded tablespoon of rooting hormone and spread it on a sheet of paper. Press the severed end and the leafless part of the snowball bush cutting in the powder until it is coated, then tap the stem to remove the excess. Discard the remaining hormone from the sheet of paper.
Stick the hormone-treated part of the cutting into the medium. Make sure the bottommost set of leaves is roughly 1/4 inch above the surface. Press the medium firmly against the stem and water again until the excess moisture trickles from the drainage holes.
Set the pot in a bright, warm area. Place softwood cuttings outdoors under dappled shade, and hardwood cuttings indoors near a bright, sunny window. Cover softwood cuttings with a large, clear plastic bag, but prop up the bag with a stick to keep it from resting against the leaves.
Maintain constant moisture in the growing medium, but let the surface dry out between waterings. Also, mist softwood cuttings daily to keep the leaves hydrated, and increase to twice daily during periods of extreme heat.
Check for roots after one month by tugging gently on the base of the snowball bush cutting. Softwood cuttings typically take three to six weeks to root, while hardwood cuttings take six to eight weeks.
Aftercare and Transplant
Newly rooted snowball bush cuttings will fail if transplanted too early. Grow them in their original pot in a lightly shaded, sheltered spot for at least two to three months, preferably longer. The rooting medium lacks the nutrient content they need for good growth. Feed them with a solution of 1/4 tablespoon water soluble, 10-10-10 fertilizer dissolved in 1 gallon of water. Apply it monthly.
Transplant snowball bushes into a permanent spot in the garden once they have produced an abundance of new leaves. In mild climates where frosts are rare, transplant them in fall. Transplant in spring well after the last frost in colder climates. Space them 5 to 15 feet apart, and spread a 2-inch layer of mulch around the base, leaving a 2-inch gap between the mulch and the trunk.
Snowball bushes need weekly during the summer, so water regularly if it hasn't rained.