The Challenge of Coping With Some Very Bad Neighbors

By Suzanne Woods

Invasive Japanese Barberry has been linked to Lyme disease.

All over Norfolk in old pastures, disturbed woodlands and along stream banks, the bright young leaves of Japanese Barberry (Berberis thunbergii) have been out for weeks. Like many aggressive invasives, barberry gets going early to get a jump on its competition. It is hard to miss. This sprawling shrub has wedge-shaped leaves clustered along the stem together with a single, long thorn (sometimes with two smaller side thorns), which keep the deer at bay. The elliptical berries ripen to red in fall along with the foliage. First brought into the U.S. as an ornamental shrub and s As a natural fence, Japanese barberry now poses a real problem in New England, as the shrub quickly establishes a dense thicket. Once it gets a firm hold, native plants are shaded out. Worse still, studies at the Connecticut Agricultural Experiment Station (Hort.uconn.edu/cipwg), have established a link between Lyme disease and Japanese barberry. White-footed mice populations, which harbor the disease and pass it to deer ticks, are significantly higher in stands of barberry than in fields and woodlands without it. It seems the same thorns that discourage browsing also discourage foxes, coyotes and other predators. So, what to do? First, be aware that there is a native American barberry (B. Canadensis), which is not a problem species. It has warty brown twigs with toothed leaves a but like a holly, and three spines of equal length rather than the one on Japanese barberry stems. At this time of year, when the ground is relatively moist, Japanese barberry can be yanked out by the roots. Once it is pulled, it can be safely chipped, bagged and dumped, or burned. The yank method won’t work for the biggest shrubs. These can be cut back. You may also treat the cut stump with a swab of Roundup. Make a 1:1 solution of Roundup concentrate and water (not the diluted spray), and using a sponge on a stick, swipe it across the cut surface. Another technique is to singe the bush with a handheld propane torch such as a Red Dragon Vapor Torch, or drip torch. Land managers often use this method for controlling invasives as an alternative to chemicals. Scorch the plant lightly, wilting the leaves, then lightly singe the ground around the base of the plant. Do this in wet weather. You do not want to start a forest fire. Mulitflora rose (Rosa multiflora) is another shrub that can make an area virtually impassable. It is native to Asia and was brought in during the 1800s. At first it was promoted as a living fence, a task it performed well with its nasty, curving thorns. It quickly overwhelms old fields and roadsides. In fact, a mature plant can produce half a million seeds that remain viable in the soil for years. The shrub has compound leaves with serrated leaflets, fragrant flowers in late spring and small red hips in late summer and autumn. If you look closely at the base of a leaf stalk, you will see a diagnostic collar of stiff hairs. Unfortunately, multiflora rose does not pull up easily and spreads by developing roots where branches touch the ground. Repeated field mowing is a good control method, but must be repeated several times a season to keep the upper hand. Spraying the plant with Roundup will also help control it. Rose rosette disease, which is native to the U.S., is spreading eastwards from the Midwest and may help to knock back multiflora rose in the future. But don’t count on it. Attack it now.