Invading Forces

In honor of my state's (New York) very first Invasive Species Awareness Week (July 6-12), I've decided to touch upon the idea of invasive species.  And although I am highlighting invasive plants of the northeastern U.S., we are by no means alone in dealing with this problem.

What exactly is an invasive species?  Wikipedia sums it up by the following:  "Introduced species (also called "non-indigenous" or "non-native") that adversely affect the habitats and bio-regions they invade economically, environmentally, and/or ecologically. Such invasive species may be either plants or animals and may disrupt by dominating a region...."

All corners of the world are affected by non-native plants.  Why is it a problem?  Because sometimes visitors move in and become very comfortable in a spot.  Not only do they decide to stay, but they begin to reproduce--and can potentially crowd out the indigenous population.  Think about it this way: you meet a visiting couple from across the globe, who seems nice enough, so you let them sleep on your couch.  They like your sofa so much, they decide to squat in your living room...and even start a family!  I know, I know: Extreme example (though I actually saw a news story similar to this involving a couple who couldn't unload a non-working nanny who barricaded herself in one of their guest bedrooms, believe it or not!), but you get the point.  Visitors good.  Invaders bad.

There is a laundry list of invaders on state and federal DEC websites, but here are the species I've noticed are among the worst offenders in my area:

Milfoil (Myriophyllum species):  Hailing from Australia, the aquatic version of this plant invades lakes and streams to the detriment of natives.  It grows very fast and fragments easily, so pulling it out can be tricky.  Of course there are chemicals to combat the problem, but since I think chemicals only cause more problems down the road, I would never recommend this method.  Hand harvesting is time-consuming, but essential for proper, permanent removal.  In New York's Adirondack Mountains, this is what they have down, with positive results.  Well-trained divers have made a huge difference, but it is an ongoing issue.  On the horizon: the discovery that an aquatic weevil (Euhrychiopsis lecontei) eats nothing but milfoil.

Lesser Celandine (Rununculus ficaria): a pretty plant with glossy, heart-shaped leaves and yellow flowers from the buttercup family.  Seems harmless enough, right?  Wrong.  This plant is truly a wolf in sheep's clothing.  Why?  It grows in a tricky, super-invasive way: bulblets are produced along the stems of the above-ground portions of the plant, but are not apparent until late in the flowering period. These little bulbs are pale and hard to detect.  If you can't see them, you can't pull them out. They survive for years and are easily moved in contaminated dirt or by water.  Lesser celandine prefers shaded to partially shaded sites though it can thrive in full sun with adequate soil moisture. Deciduous woods are an excellent habitat for this species enabling the plant to thrive.   Dense patches form, crowding out early-blooming native wildflowers. To the private landowner or gardener, lesser celandine escaping from plantings quickly overwhelm flowerbeds and lawns. Contaminated garden loam applied to new lawns can create problems in a few short years. Because of the bulbous nature of the root system, control can be difficult.  Sadly, cultivars of lesser celandine continue to be sold through catalogs and nurseries nationwide.

Japanese Barberry (Berberis thunbergii): a shrub with thorns and berries, ideal for attracting and nourishing bird populations, this plant can spread quickly and easily grow out of control.  A former professor of mine explained that this species is actually banned for sale in Connecticut due to its invasive tendencies.

Japanese Bittersweet (Celastrus orbiculatus): a vine that is quite lovely to look at, it's often used to make garlands and wreathes.  Unfortunately, in forests and homeowners' gardens, it can become too much of a good thing.  Oriental bittersweet is a vigorously growing vine that climbs over and smothers vegetation which may die from excessive shading or breakage. When bittersweet climbs high up on trees the increased weight can lead to uprooting and blow-over during high winds and heavy snowfalls. In addition, Oriental bittersweet is displacing our native American bittersweet (Celastrus scandens) through competition.  If you must grow this vine (though I'd opt for the native version, which is just as lovely), keep it controlled through vigorous pruning.