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Worst Invasive Plants

List of Species to Be Most Wary Of

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Photo: a Scotch broom with yellow and orange blooms.

Picture: Scotch broom (Cytisus scoparius) is an aggressive spreader and has been classified as a noxious weed in some parts of the U.S.

David Beaulieu

Some invasive plants may be ugly, depending upon whom you ask. For instance, at the end of the growing season, Japanese knotweed litters the landscape with ragged dead canes that I, myself find to be about the closest thing to "trash" that the natural world produces. But the collectors who brought these thugs to the West in the first place did so for what they considered to be their ornamental quality, of all things (there's no accounting for taste!).

And that's how many of the examples in my picture gallery of invasive plants first breach enemy walls: they're invited in as ornamentals, with warmth and fanfare. Good looks make their conquest a breeze. Fact is, the invader doesn't always assault the gates wearing a horrific visage and battle scars.

Some of the invasive plants listed below are quite attractive. Take burning bush, that exotic (or "alien") shrub from Asia. Few shrubs put on a better fall foliage display. Another fall star is the vine, sweet autumn clematis. But the attractive invasive plants are like some of the good-looking people one meets (you know the type): once we get past the exterior and learn more about them, we realize we wouldn't necessarily want them hanging out in our yards. Looks, after all, can be deceiving.

Invasive plants can be thought of as exotic specimens "gone wild," as in "out of control." The following list of invasive plants comprises a collection convenient for introductory purposes; I call it "The Deceitful Dozen." It is obviously not meant to be an exhaustive list, nor would I in any way deny that such invasive plants as purple loosestrife and kudzu have perhaps rendered more harm to native habitats than any of the twelve examples on my list. The list was inspired mainly by some of the worst offenders that I commonly encounter in yards in my home territory in the U.S., New England.

But don't stop reading, just because you, yourself don't live in New England. The aliens colonizing my region are known as marauding invaders in other regions, too. In fact, one of my examples, lantana, earned its "invasive plant" label far to the south of New England, where the weather is warm enough to sustain it as a perennial. Nor are warnings about these twelve problem children pertinent to North America alone; e.g., Japanese knotweed is widely recognized as a menace in the United Kingdom.

Bittersweet

There are three "bittersweets," and this article distinguishes between them: oriental bittersweet, American bittersweet and bittersweet nightshade. The oriental bittersweet vines are sure to make any list of worst invasive plants in North America.

Read article: Bittersweet

Wisteria

As with bittersweet, so with wisteria: the North American grower must distinguish between American wisteria vines and their Chinese counterparts.

Read article: Wisteria

English Ivy

If you wished to crowd out weeds in an area of your landscape, you'd be delighted to hear about a vigorous ground cover -- an attractive vine that tolerates shade -- right? That description fits English ivy perfectly. But that's the problem: English ivy is too vigorous, earning it a spot on my list of worst invasive plants.

Read article: English Ivy

Sweet Autumn Clematis

Like the preceding three vines, sweet autumn clematis is also another of those "good-looking" specimens about whose charms I warned you. Perhaps making its apparent innocuousness even more convincing is the presence of the word, "sweet" in its name. But this is no sweet little wallflower!

Read article: Sweet Autumn Clematis

Ajuga

My fifth entry in this invasive plants list is yet another vine (albeit a smaller one): the mat-forming ajuga (or "bugleweed"). Like English ivy, it is a common ground cover; another popular ground cover with thuggish tendencies is the sweet-smelling lily-of-the-valley. But because of its combination of pleasing blossoms and weed-suppressing capability, ajuga's siren song may be the most powerful of the three.

I could easily go on and name more names when it comes to thuggish vines: they are perhaps the least well-behaved class of landscape plants. For example, Japanese honeysuckle is notorious for spreading beyond the bounds within which one might wish to contain it.

Read article: Ajuga

On Page 2 my list of worst invasive plants continues, as we switch focus from vines to shrubs....

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