The first frost has hit. Its delicate layer can be a mighty match for some invading plants. As tough as Japanese knotweed is during spring and summer, for instance, it is easily weakened by freezing temperatures. Other plants, like Japanese barberry, seem to shine during this time.
Japanese barberry's architecture, fruit and color - not to mention its deer deterring spines - make it a favorite ornamental planting of nurserymen, landscapers and homeowners. In late October and November, its leaves look like a sunset of oranges and reds in the forest when most other trees and shrubs have lost their leaves.
Wait, "a sunset in the forest"? That's right. Japanese barberry is one of those pesky plants that just won't stay put. Though some are camouflaged green in the summer, in the fall they look like glowing red orbs and are easily spotted.
Japanese barberry spreads in a forest in Keene.
(Photo — Brendan Quirion)
A closeup of Japanese barberry red fruits.
(Photo — Leslie J. Mehrhoff, University of Connecticut, Bugwood.org)
Barberry is a more noticeable garden escapee in the Hudson Valley than in the Adirondack region. It runs rampant along forest edges and in the forest understory; however, each passing year it becomes more apparent in the woodlands of the Champlain Valley.
I've noticed it spreading on my own property in Saranac Lake, too. When we bought our home, we inherited the previous owners' troublesome beauties: European honeysuckle, Oriental bittersweet, Norway maple and others, including Japanese barberry. Most of our lot is wooded, and I became concerned when I saw baby barberry plants sprouting up throughout the woods. Left untended, these shrubs can grow to greater than 8 feet in height and 10 feet in diameter and form dense, spiny, impenetrable thickets.
Barberry is shade tolerant, drought resistant and adaptable to a variety of open and wooded habitats, wetlands and disturbed areas. It prefers to grow in full sun to part shade but will flower and fruit even in heavy shade. This puts our forests at risk and is cause for concern. Barberry alters soil pH, nitrogen levels and biological activity in the soil. Once established, barberry displaces native plants and reduces wildlife habitat and forage.
Luckily, if detected when they are small, barberry plants are very easy to pluck out of the ground. Barberry has shallow roots so it can be pulled, preferably when the soil is damp and loose, using thick gloves to avoid injury from the spines. It is important to get the entire root system since this is one way that it spreads. Mechanical removal using a shovel, hoe or Weed Wrench can be very effective for uprooting larger or older shrubs, which can also be mowed or cut repeatedly. Seedlings and small plants pulled or cut can be left on site with roots exposed. Larger plants can be used as firewood, chipped or burned.
Japanese barberry also spreads by seed, so removing plants prior to late summer seed set is best. Large numbers of seeds plus a high germination rate, estimated as high as 90 percent, give barberry a competitive survival rate. The seeds are transported to new locations with the help of birds (e.g., turkey and ruffed grouse) and small mammals. Birds frequently disperse seed while perched on powerlines or on trees at forest edges.
Because Japanese barberry (Berberis thunbergii) has been cultivated for ornamental purposes since the late 1800s, a number of cultivars exist for sale (more than 400 Berberis varieties). Leaves can be green, bluish green or dark reddish purple, and some studies show that plants can change from one color to another in wild conditions. The fruits are bright red berries that mature during late summer and fall and persist through the winter.
Japanese barberry is still sold. Your choice matters. Many attractive native shrubs are available that make great substitutes for Japanese barberry. A few examples include bayberry (Myrica gale), winterberry (Ilex verticillata) and ninebark (Physocarpus opulifolius). If you're planning a new landscape project, or considering swapping out an invasive ornamental in your garden, please check with your plant nursery for suggestions for non-invasive plants appropriate to your area.
As the growing season comes to a close, so does another season of "Eye on Invasives." See you in the spring.
'Eye on Invasives' is a biweekly column that spotlights a top invader when it is easiest to identify. The Adirondack Park Invasive Plant Program is a partnership program housed at the Adirondack Chapter of The Nature Conservancy in Keene Valley.
Find out more about this award-winning program online at www.adkinvasives.com.