CTEC 6/6/06                   Invasive Species

“Invasive species” are plants that are able to thrive and spread outside their natural range; our forests, streets and gardens are filled with them. They are often able to gain an ecological edge, since the insects, diseases and foraging animals that naturally keep their growth in check in their native habitat are not present here. Some invasives spread so fast that they crowd out most other plants, changing forests, meadows or wetlands into a landscape dominated by one species. This is neither healthy nor desirable.

THE WORST INVASIVE OFFENDER

The worst invasive offender in our area is a showy, spiky flower called Purple Loosestrife (Lythrum Salicaria). In the same way as the American south is being overrun with kudzu, Purple Loosestrife is our biggest plant bully. Although attractive to the eye, Purple Loosestrife causes ecological havoc, invading wetlands and altering water chemistry so that amphibians, such as toads, don’t develop normally. It also crowds out the native cattails, which are essential to many birds’ nest-making. Sadly, Purple Loosestrife is still sold at some garden centers. The best defense against it is to cut it down when it blooms; even a partial root left in the ground is likely to re-grow.

OTHER INVASIVE SHRUBS, FLOWERS, VINES

Other invasive offenders include Japanese Barberry, Asiatic Bittersweet, Autumn Olive, Japanese Knotweed, Common Reed, Multiflora Rose, Porcelain Berry, the above-mentioned Kudzu Vine, and the Tartarian, Japanese and Amur Honeysuckles. Garden favorites like English Ivy, Exotic Wisterias, Periwinkle, Day Lily, Winged Burning Bush, Butterfly Bush, and Mimosa Tree are not native to the area and, although beautiful, are ecologically disastrous if not controlled. (For scientific names, see below.)

TREES TO AVOID

Our area's major invasive trees are Norway maple (Acer platanoides), Princess tree (Paulownia tomentosa), Tree of heaven (Ailanthus altissima), Mimosa Tree (Albizia julibrissin), Sawtooth Oak (Quercus acutissima), Black Locust (Robinia pseudoacacia), and Bradford Pear (Pyrus calleryana). Norway spruce is not native to North America (and, although it doesn't spread and invade natural areas, it is vunerable to blowdown and has been overly planted in our region).

STILL SOLD

Many garden centers and landscaping companies still promote and sell invasives. Bring this list with you when you shop for plantings or plan any landscaping,  so you'll have a handy list of what species to avoid. Keep in mind that some invasives are controllable with consistent attention to restricting their area of growth and pruning them back frequently. When in doubt, consult an arborist; not only will you benefit the ecology and environment, but you may save yourself a lot of garden work as well as money spent watering thirsty invaders.