LSU AgCenter's Weekly Message

Revisiting Viburnums

Viburnums, as a group, have long been a bit nebulous to me. My interest in them was piqued recently when I purchased a southern arrowwood (Viburnum dentatum) from the Tangipahoa Parish Master Gardener Association at the LSU AgCenter Hammond Research Station’s Fall Garden Day and Plant Sale. I chose the variety ‘Ben’s Creek’ because of its origin. It was propagated from a plant collected by nurseryman Rick Webb near its namesake in Washington Parish. Of course, I want all the plants named after locations in my home parish. (I already had ‘Bogalusa Highway’ yaupon.)

Southern arrowwood is native to much of the eastern US. Within Louisiana, it’s found in the Florida Parishes and the western half of the state. Southern arrowwood is deciduous and grows to approximately 8 feet tall, though it can get larger. Like many viburnums, it produces a flower cluster with white petals in the spring. The flower clusters reach 4 to 5 inches wide. Blue-black fruits suitable for birds form if adequate cross-pollination occurs. The plant can grow in partial shade to full sun. In the wild, southern arrowwood is often found in moist woods and along stream banks.

Another viburnum native to the Florida Parishes is possumhaw (V. nudum). (Note that this is different from the deciduous holly, Ilex decidua, that’s also called possumhaw.) This plant tends to grow on wetter sites than southern arrowwood does. Like southern arrowwood, possumhaw is deciduous and produces a white (or off-white, for possumhaw) flower cluster in the spring. It sometimes flowers in the fall, too. Fruits turn from green to pink to blue-black over time. Possumhaw has smoother leaf margins than other native viburnums, and leaves tend to be glossy. It typically reaches about 10 feet tall but can grow larger.

Several other viburnums – including mapleleaf viburnum (V. acerifolium), blackhaw (V. prunifolium), and rusty blackhaw (V. rufidulum) – are native to Louisiana but more commonly found in the northern half of the state.

Among non-native viburnums, one of the best-known in Louisiana is Chinese snowball viburnum (V. macrocephalum). In spring, this shrub produces flower clusters that resemble those of panicle hydrangeas but are more rounded. Petals are light green when they first appear and become white over time. Chinese snowball viburnum sometimes flowers in fall, also. It can grow to 15 feet tall or greater. Flowers are sterile so, unlike most other viburnums, it does not produce fruit. Leaves are semi-evergreen in Louisiana.

Another viburnum planted in southern Louisiana is sweet viburnum (V. odoratissimum). This is a fast-growing evergreen shrub that’s sometimes used as a hedge. It can grow to approximately 15 to 20 feet tall. Sweet viburnum sometimes experiences cold damage in USDA Hardiness Zone 8. Like other marginally hardy plants, it shouldn’t be pruned or fertilized in late summer, since these activities can encourage growth that lacks cold hardiness.

‘Mrs. Schiller’s Delight’ viburnum is a Louisiana Super Plant. It’s a cultivar of the species known as small viburnum, Walter’s viburnum, or small-leaf arrowwood (V. obovatum). The species is considered native to the southeastern US though not to Louisiana. The small viburnum gets its name from the size of the leaves. The plant itself can get quite large. ‘Mrs. Schiller’s Delight’, however, is a compact variety that reaches approximately 5 feet tall if unpruned. The white flower clusters are not as large as those of some viburnums, but ‘Mrs. Schiller’s Delight’ produces an abundance of them in spring. It grows in partial shade to full sun, but afternoon shade is likely beneficial. The plant is considered evergreen in Louisiana.

I’ll make a final note about viburnums in general. One characteristic that’s often used when identifying plants is leaf arrangement. Alternate leaf arrangement is most common, with opposite and whorled arrangement being less so. Because viburnums have oppositely arranged leaves – meaning that two leaves will occur across from each other on stems – this can be helpful in the process of determining if a plant is a viburnum or not.

Let me know if you have questions.

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Dr. Mary Helen Ferguson is an Extension Agent with the LSU AgCenter, with horticulture responsibilities in Washington and Tangipahoa Parishes. Contact Mary Helen at mhferguson@agcenter.lsu.edu or 985-277-1850 (Hammond) or 985-839-7855 (Franklinton).