Non-Native Invasive Species

Multiflora rose

Rosa multiflora

Multiflora rose

Multiflora rose
Photo: James H. Miller, USDA Forest Service, Bugwood.org

The story of multiflora rose is one of unforeseen consequences. It was first brought to North America from Japan in 1886 to be used as an understock for ornamental roses. Beginning in the 1930s, it was promoted by a variety of agencies as a "living fence," a glare-reducer and crash barrier on highway medians, and a source of food for wildlife. Now the species fills abandoned or tired agricultural fields and adjacent woods throughout much of North America, except where it is very cold, very warm, or very dry. Multiflora rose is the two-hundred-pound Godzilla of the plant kingdom.

Why? Like many invasive plants, it reproduces unusually successfully. Each plant produces thousands of fruits each year. Birds love these "rose hips" and spread the seeds everywhere they go (the seeds seem to germinate best after passing through bird bodies). And the species can also reproduce vegetatively, when its arching branches touch ground and readily take root.

Multiflora rose

Multiflora rose
Photo: James H. Miller, USDA Forest Service, Bugwood.org

Multiflora rose is endowed with a number of very tough survival mechanisms. Cut it back or burn it up and it resprouts. Pull it out and formally dormant seeds germinate in the newly disturbed earth. Animals won't browse it for its thorns. People avoid it for the same reason.

And it has few lethal pests. One very important exception is a native disorder, perhaps a virus (no one has yet been able to raise the disease in the laboratory), called rose rosette disease. Symptoms include distorted leaves and branches and a reddening of the leaves. The disease was first discovered in Canada and the Midwest. It is now found as far east as Pennsylvania and West Virginia. Infected multiflora rose plants often die within one to two years.

Multiflora rose

Multiflora rose
Photo: James H. Miller, USDA Forest Service, Bugwood.org

Rose rosette disease might seem to be good news - a new biological control for this awful plant pest. It is true that the disease has killed large stands of the plant in the Midwest, but only those growing in full sun. Apparently the mite that spreads the disease is not active in shaded areas. This means that sources of seed will persist, and that re-infestation will be likely. Perhaps most discouraging is the fact that all roses - including cultivated ones - are susceptible to lethal infection by this pathogen.

The best ways to control multiflora rose seem to be repeated mowing (mature plants may need to be knocked over or pulled out with a tractor first), the use of herbicides such as Roundup™, and constant monitoring for new seedlings. But if you pursue these onerous tasks in June, you might reward yourself by stopping to smell the roses. One unambiguously nice thing can be said about this plant: right now its flowers smell heavenly.