[AG-EQ] 16 Invasive Plants to Avoid

[Tracy Carcione]

That was interesting.  I have some of these buggers, though my English ivy is not running too badly amok.  Still, I may try pulling it out and leaving the Virginia creeper, which does a lot of the same things without getting too rambunctious about it.
Personally, I'd add Rose of Sharon to the list.  It's pretty, and the bees use it some, but I pull out lots of seedlings every year.  Which is how I got my bush; I didn't pull out the seedling that landed in my yard.
Tracy



-----Original Message-----
From: AG-EQ [mailto:ag-eq-bounces at nfbnet.org] On Behalf Of dogwood farm via AG-EQ
Sent: Tuesday, May 05, 2020 12:52 PM
To: Agricultural and Equestrean Division List
Cc: dogwood farm
Subject: [AG-EQ] 16 Invasive Plants to Avoid

16 Invasive Plants to Avoid
Written by David Beaulieu, garden writer

An invasive plant can be defined as any plant that grows where you
don't want it to and does it in a way that makes it hard to control.
It doesn't have to be a weed, and invasive plants are by no means
always ugly specimens. A lot of it depends on the setting. For
example, bittersweet vines in some settings can be quite beautiful and
desirable, but if they take over your woodland garden, they are a
nuisance indeed. And some plants begin as perfectly desirable
landscape species that you plant deliberately, such as obedient plant
(Physostegia), only to prove their invasive nature in a year or two
when you discover their rampant growth characteristics.

Some invasive plants listed are quite attractive. Consider burning
bush (Euonymus alatus) for example—an exotic (or "alien") shrub from
Asia. Few shrubs put on a better fall foliage display. Another fall
star is the vine, sweet autumn clematis (Clematis terniflora). A
summer standout is Scotch broom (Cytisus scoparius). But attractive
invasive plants are like some of the good-looking people one meets
(you know the type): Once you get past the exterior and learn more
about them, you no longer want them to hang out. Looks, after all, can
be deceiving.

Many invasive plants can be thought of as exotic specimens "gone
wild"—as in "out of control." The following list of 16 invasive plants
comprise an introductory collection, but it is by no means an
exhaustive list. Remember, too, that invasives tend to be defined
regionally. Some species that pose no problems at all in some areas
behave in true invasive style in other regions. Some plants are
seriously invasive in the warmer climates where they are perennial but
are no problem at all in colder regions where they are killed off each
year.

1. Bittersweet
There are three "bittersweets," and it is important to distinguish
between them: oriental bittersweet (Celastrus orbiculatus), American
bittersweet (Celastrus scandens), and bittersweet nightshade (Solanum
dulcamara). It is the Oriental bittersweet vine that is sure to make
most lists of worst invasive plants in North America. The other forms
can also be invasive but are less so than oriental bittersweet.
American bittersweet is the form with attractive red/orange berries
that are often used in decorative displays. All forms of the plant are
toxic, however, and should be avoided in the landscape.

2. Wisteria
As with bittersweet, so with wisteria: The North American grower must
distinguish between American wisteria vines (Wisteria frutescens) and
their Chinese counterparts (Wisteria sinensis var.). While both types
are robust growers, it is the Chinese wisteria that poses a truly
invasive danger south of USDA hardiness zone 4.

3. English Ivy
If you wished to crowd out weeds in an area of your landscape, you
would expect to be delighted to hear about English ivy (Hedera helix),
a vigorous, attractive ground cover that tolerates shade. That
description fits English ivy perfectly. But that's the problem:
English ivy is too vigorous, earning it a spot on the list of worst
invasive plants. It easily escapes landscape cultivation and is
regarded as a seriously problematic invasive, especially in the
Pacific Northwest.

4. Sweet Autumn Clematis
Like the preceding three vines, sweet autumn clematis (Clematis
terniflora) is another of those "good-looking" specimens that can
overwhelm a landscape. It is especially problematic in the East and
lower Midwest. While this plant does have a very sweet odor, that's
the only thing pleasant about it. Clematis paniculata is sometimes
sold as sweet autumn clematis, but this is a less invasive vine that
comes from New Zealand. It is C. terniflora that you need to be
careful with.

5. Ajuga
The mat-forming ajuga (Ajuga reptans), also known as bugleweed, is
another popular ground cover that can turn thuggish (lily of the
valley is another). Because ajuga has pleasing purple blossoms and the
ability to suppress weeds, it is often planted in shady areas as a
ground cover. Many homeowners, though, come to despise it when it
begins to take over a garden or lawn.

Ajuga is especially problematic in warmer climates where there is no
winter frost to kill the plants back annually.

6. Barberry
The barberry shrubs (Berberis spp.) have assaulted North America from
two sides. One type, Berberis thunbergii, is from the Far East; the
other, Berberis vulgaris, from Europe. These invaders have come armed
to the teeth, bristling with the thorns that have made them so useful
in many a hedge. B. thunbergii, usually known as Japanese barberry, is
so invasive that much of the Midwest has placed it on a list of
dangerously invasive plants, strongly suggesting that it should never
be planted at all.

7. Burning Bush
In autumn, burning bush (Euonymus alatus) puts on a show for the ages,
bearing red or pinkish-red leaves. Colorful reddish-orange berries
accompany the striking foliage. So why is burning bush one of the most
hated exotic plants among gardeners "in the know"? This shrub is
considered dangerously invasive across much of the northern United
States from Maine to Minnesota, as well as in the Southeast.

8. Lantana
Lantana (Lantana camara) is a broadleaf evergreen shrub native to
tropical areas, and it is a notable invasive in Florida and Georgia
and across the South all the way to California. But it poses no danger
in colder climates north of zone 9, where it is often used in hanging
baskets. In warm zones, however, it can easily escape gardens and
naturalize in dangerous profusion.

9. Butterfly Bush
Butterfly bush (Buddleja spp.) is among the worst invasives in the
Pacific Northwest, where growing conditions resemble its native
habitat. It also an invasive problem in areas of the Southeast. In
areas colder than zone 6, it is less problematic, since the plant dies
back to the ground each winter. An alternative plant to grow for
attracting butterflies is butterfly weed (Asclepias tuberosa).
Butterfly bush is so-named because it attracts butterflies (as well as
other pollinators), but to humans, the plant is somewhat unpleasant in
odor.

10. Common Privet
As with barberry, a privet hedge is a familiar sight. That very
familiarity of privet (Ligustrum vulgare) may make it difficult to see
such exotic plants as invasives, but this species is on official lists
of problematic plants in much of the Midwest and Northeast from
Pennsylvania north to Maine. Privet's popularity is based on the fact
that it responds well to pruning and tolerates the pollution that
typically plagues plants in urban settings. But privet shrubs grow so
fast that they can easily escape the boundaries of cultivation and
become naturalized in the wild.

11. Norway Maple Trees
Full-sized trees can be invasives, too, as in the case of Norway maple
(Acer platanoides), which is considered invasive in much of the
Northeast, and dangerously so in Maine, Vermont, New Hampshire, and
Massachusetts. Originally planted as a landscape species, its seeds
easily disperse on the wind to naturalize in other environments.

12. Japanese Knotweed
Japanese knotweed (Fallopia japonica) is a clumping perennial plant
that has virtually no redeeming landscape value. The best that can be
said for its appearance is that it produces a fluffy-looking flower in
early autumn (thus one of its alternate common names, "fleece
flower"). The opinions of 19th-century plant collectors
notwithstanding, most 21st-century Westerners agree on this one:
Japanese knotweed is an ugly nuisance and an easy pick as one of the
worst invasive plants. It is considered invasive in every state,
though is more so in its natural hardiness zones, zone 5 to 9.

13. Kudzu
Kudzu vine is in the pea family. So far, so good, right? After all,
you're familiar with peas from your experiences at the dinner table.
Along those lines, kudzu has even been employed as livestock feed. But
this perennial vine from Asia is one of the very worst invasives of
all time, and is sometimes ruefully called "the vine that ate the
South." It is an enormous problem in all Southern states. Initially
planted to shade porches on southern plantations, the plant quickly
spread to surrounding territory, where it now gobbles up nearly all
that it touches. It grows well in both sun and shade and is
dangerously invasive throughout the South and Southeast and well up
the Atlantic seaboard.

A recent control effort involves bringing goats into areas infested
with kudzu and turning them loose to eat their fill.

14. Tansy
Tansy, unlike the exotic plants considered above on this invasive
species list, is an herb—albeit a poisonous one. Tansy's toxicity
belies a rich tradition of medicinal and culinary usage. But there's
more to worry about than just its toxicity: Tansy plants are invasives
that spread via both seeds and rhizomes.

15. Purple Loosestrife
Purple loosestrife is an invader of wetlands. Many people who have no
clue about the name of the plant have nonetheless seen it innumerable
times and remarked upon its beauty. In fact, it is a lovely plant when
massed together—which is the norm, since this is a plant that spreads
incredibly vigorously.

Purple loosestrife is thought to arrive in North America as seeds in
soil used as ballast in sailing ships in the early 19th century. Now,
200 years later, it is found in every state in the United States,
except Hawaii and Alaska. The plants take over wetlands by forming
dense root mats that choke out native plants, degrading wildlife
habitat. Since 1992, the governments of Canada and the United States
have used to European beetles, Galerucella calmariensis and G.
pusilla, to feed on the plant—an experiment that appears to be
successful.

16. Japanese Honeysuckle
Japanese honeysuckle (Lonicera japonica) is another attractive,
sweet-smelling specimen that turns out to be a sinister foe. This
vigorous, fast-growing twining vine has fragrant yellow flowers that
appear from June to October, and it grows to 30 feet. When planted
deliberately, it is used as a ground cover, but it is considered an
exotic invasive across the entire Midwest.

If planted in the garden, great care should be taken to keep the plant
in check, including aggressively cutting it back regularly. When it
escapes, this plant can break tree limbs with its heavy weight and
kill shrubs and trees by girdling them with strong vines.

Susan
dogwoodfarm62 at gmail.com

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