Invasive plants can survive tough environmental conditions. Shade? Not an issue. Drought? No problem. Poor soils? Bring it on. Disturbance? The more, the better.
Weather-related disturbance, like flooding, is of particular concern following a year of record rains. Hurricane Irene's floodwaters ripped through rivers and streams. Fast- moving waters in unprecedented volumes scoured banks and carried much in its path, including invasive plants such as Japanese knotweed. This summer keep watchful eyes along your favorite river for new growth of this tenacious and aggressive plant.
Natural disturbance events have always occurred, but the spread of invasive plants is a recent unintended consequence. Early colonizing plants are first on the scene after a disturbance, followed by hardier, taller growing species that shade them out and so on. The proliferation of invasive plants changes the natural succession of natives, and, instead, puts these highly competitive non-native plants at the ready to invade.
Why is Japanese knotweed of particular concern? First, it grows along riverbanks and second, it spreads by fragmentation. Any small portion of stem or root can become a new plant - a recipe for disaster following an extreme flood event.
We often see Japanese knotweed in roadside ditches, waste areas and on private lands as an intentional hedgerow or an unfortunate annoyance. Plant fragments are accidentally introduced in infected soils or infestations worsened through misguided management efforts. Where knotweed wreaks the most havoc, however, is along rivers and streams. Dense canopies of knotweed can extend for miles, muscling out natives with its rapid growth, broad foliage and extensive root network. When growing along stream banks, knotweed can destabilize soils, causing erosion and sedimentation that deteriorates water quality and fish habitat.
Landowners and land managers from central New York, the Champlain Valley and Vermont reported seeing knotweed spreading along rivers after last fall's flooding and again this spring. The exposed soils and the loss of native vegetation created a prime habitat for knotweed to take hold. How did these invading plants get there? Fragments may have washed downstream or been inadvertently introduced on machinery or materials used during emergency response and restoration efforts.
"Ask APIPP" is a new feature that will address readers' questions about invasive species, such as identification, impacts or management, or solutions to combat their spread.
Submit questions via email to the Adirondack Park Invasive Plant Program. Include "Ask APIPP" in the subject heading and send your question to firstname.lastname@example.org. Questions and answers will be considered for publishing in the biweekly "Eye on Invasives" column.
The most important thing to do now is to be on the lookout for new populations. Detecting infestations early provides the best chance for successful elimination. If you are on a river, keep an eye out for thick, reddish-green, bamboo-like stalks growing to heights of 10 feet with alternating, oval-shaped leaves. If possible, take note of the locations with a GPS. Although it may be tempting to start management now, if the population is too large to handpull or dig out, it is most effective to treat later in the summer, just as plants begin to flower.
Another action to take is to replant disturbed areas with native trees and shrubs suitable to streamside conditions, like red-stemmed dogwood or silver maple. Putting into place desirable vegetation will take up space that otherwise might be available for invasives to take root.
It is likely that we will continue to see erratic weather patterns and, with them, the accelerated spread of invasive plants. Contact the Adirondack Park Invasive Plant Program at 518-576-2082 to report sightings of Japanese knotweed along your favorite river in the Adirondacks, for a list of suitable streamside native trees and shrubs to plant, or to get involved in our early detection and management programs.