April 2017

Choose Your Viburnums with Care

Contact: Sylvan Kaufman Sylvan.Kaufman@gmail.com

Doublefile viburnum (Viburnum plicatum tomentosum) Richard Webb, Bugwood.org

ANNAPOLIS, MD (April 01, 2017) - Gardeners love viburnums for their white spring flowers, compact growth, and colorful fall fruits and foliage. Few gardeners know that some viburnums have become invasive plants and should be avoided. Linden viburnum (Viburnum dilatatum), doublefile viburnum or Japanese snowball (V. plicatum), and Siebold viburnum (V. sieboldii) have all escaped into natural areas in the Mid-Atlantic and threaten native plant and animal species. Horticulturists introduced these viburnums from Japan and China starting in the 1800s. They were first noticed escaping around some of the botanic gardens where they were originally planted. Many of these species are coming into bloom in late April into May, and so have been chosen as the Maryland Invasive Species Council's Invader of the Month for April.

Natural areas managers are alarmed at the rapid spread of these non-native viburnums, although scientists are still learning about their potential impacts. These viburnums produce numerous red to black fruits that are eaten and dispersed by birds. They grow in sun to part shade, often invading along the edges of forests and in gaps in the forests. Once established, the shrubs can form dense thickets that keep other plants from growing. Although the shrubs provide food for birds, which disperse the seeds, viburnums may prevent a more diverse array of plants from growing that would support a greater variety of bird and animal species.

If you have one of these viburnums in your yard, consider cutting off the fruits before they mature to prevent them from spreading. If you want to remove the shrubs, seedlings can be hand-pulled and older shrubs can be cut and the roots dug out by hand or with a weed wrench. For larger plants, herbicide is usually applied to the cut stems, because plants can resprout from existing root systems.

Viburnum plicatum f. tomentosum in fruit July 2016, photo courtesy of K.L.Kyde

Outside of planted and maintained gardens, viburnums can be hard to distinguish from one another. One of the best keys currently available is Cornell University's publication on viburnum leaf beetle, a damaging leaf skeletonizer of many native and exotic viburnums. The key has detailed descriptions of multiple viburnum species. It is available online as a downloadable PDF, click here.

In the Mid-Atlantic, we have several wonderful native viburnums that can be planted in gardens. The smallest variety is arrowwood viburnum (V. dentatum). This viburnum produces beautiful blue fruits in the fall. Possumhaw viburnum's (V. nudum) fruits change color from pink to blue to purple as they mature and the shiny leaves turn deep purple in fall. Mapleleaf viburnum (V. acerifolium) is a good plant for dry shade and its leaves turn shades of pink and red in the fall. One of the largest native viburnums is blackhaw viburnum (V. prunifolium), which can be trained to grow as a small tree.

For more information about other Invasive Species of Concern in Maryland, visit the Maryland Invasive Species Council or call the Maryland Department of Agriculture at 410-841-5920.

Species Profile Sheets:

Doublefile viburnum, Viburnum plicatum. Pennsylvania DCNR.

Siebold viburnum, Viburnum sieboldii. Pennsylvania DCNR.

Linden viburnum, Viburnum dilatatum. NPS, National Capital Region.