The delightful viburnum, at home in many gardens, can defy definition with a myriad of variations from species to species. Species of viburnum can range from fruiting to flowering, trees to shrubs, with serrated leaves to lobbed leaves, and can have any variety of bud formations. In fact, there may be as many as 250 species worldwide. Propagating viburnum, however, isn't nearly as difficult as attempting to define this beautiful, decorative plant.
Several methods of propagation can be used with viburnums: some easy, some a little more involved. No matter how these plants are started, growers can be satisfied by seeing their efforts produce blooms and beautiful foliage in just a few years.
Growing viburnum by seeds is an involved and lengthy process. Viburnum seeds can take up to 18 months to germinate.
Start the seeds by warm stratifying (mimicking a warm, summer environment) for 2 months. To warm stratify, place seeds in wet sand in a sealed plastic bag and keep at 76 to 86 degrees. Next, cold stratify (mimicking the winter environment) by placing the sealed bag in a refrigerator for 3 months, opening the bag once a week to exchange air.
Plant in seeding trays in a cold frame, or covered outdoors. Transfer seedlings to individual pots filled with potting soil, then plant in late spring.
Viburnum respond well to propagating by means of softwood cuttings. Richard Jauron, with Iowa State University's Department of Horticulture, suggests taking softwood cuttings in late May or early June. Cut a segment about 4 to 6 inches, using a sharp knife.
Remove the lower set of leaves, creating a scar area. This scar area will be where the new roots form. Insert the base of the stem past the scar area into perlite or sand. Keep planting medium well watered and drained. Place a glass jar or plastic bag over the cuttings to prevent loss of moisture.
In 6 to 8 weeks, once roots have formed, remove the protective covering and let sit for 2 days, then transfer to pots filled with potting soil. Plant in the garden after 2 to 3 weeks.
Layering is the simplest of all methods to propagate viburnum. Start the layering process in the spring, when the plant is supple with new growth. Select a low-lying young branch and bend it to the ground. With a sharp knife, make a 2-inch lengthwise cut along the underside of the stem.
This nicked area will be the site of new root formation. Press the cut area into the ground and hold it in place with a stone heavy enough to keep the branch bent. In 6 to 8 weeks, roots will have formed. Cut the branch, leaving 12 inches of stem extending past the new root formation.
If roots have grabbed hold of the soil, use a clean trowel to dig around perimeter of newly forming root ball. Pot in container filled with potting soil. Transplant to garden at the end of summer.