Identifying and rooting out invasive plants

By Lynette L. Walther | Aug 11, 2017
Photo by: Lynette L. Walther Dames rocket blooms in late spring with pretty pink flowers. But don’t let this pretty face fool you; dames rocket (Hesperis matronalis) can be invasive.

There’s nothing like an official list to get a procrastinator like me into gear. After years of indecision, I finally took out the big old multiflora rose along the driveway. Who knows how long it had been there? But it was well established decades ago when we bought our old cottage. Each spring, that rose would be covered with fragrant little white blooms, and for the first few years here it was one of the few things blooming. So, there was a bit of nostalgia and affection for that old bush. Its removal required a pruning saw to cut back the many limbs and branches.

But now the deed is done. It is gone. Whew! I already am feeling better for having done it, because it is one of the plants on an invasive species list for Maine. I know that even though there was only one of them in my tiny yard, every spring I still pulled out many of the multiflora rose seedlings that managed to seed themselves into my flower beds. And if there were so many here, I expect they were spread far and wide from that one bush in my yard.

That’s the problem with invasive plants. There may be just one in the neighborhood, but their seeds are often spread by wind or animals, and they can take over new territory quickly. It has been a while coming, but Maine has finally established a list of prohibited invasive plants as of the first of this year. To be fair, it takes a while to investigate and define invasive plants, and notify nurseries that might be growing those species that they can no longer be sold.

What this list does is prohibit the selling, importing, exporting, buying or intentionally propagating for sale a list of 33 invasive plants, shrubs and trees. According to a fact sheet from the Maine Department of Agriculture, Conservation and Forestry, also includes cultivars, varieties and hybrids of the listed plants.

There may be variances granted for scientific research or for varieties, cultivars or hybrids that “have been shown to not be invasive through peer reviewed scientific research,” and the plant rule and prohibited plant list is to be reviewed every five years.

So, what exactly is an “invasive” plant and why have they been banned? Wikipedia defines an invasive as: “…a plant that is not native to a specific location (an introduced species), and which has a tendency to spread to a degree believed to cause damage to the environment, human economy or human health.”

If only these invasive plants were ugly and grew poorly here, our challenge would not be so great. But these invasive plants are attractive and grow well in landscapes, which is how many of them became established originally. Indeed, it is that vigor and rapid growth that singles them out and which has enabled them to dominate vast areas.

Most often the way that works is that an invasive plant (say, purple loosestrife, or burning bush) is introduced by someone finding it attractive or useful in some way, and it gets planted in a landscape or for some purpose. The voracious southern vine kudzu is an example of a plant introduced to prevent erosion, the same as the multiflora rose, which was used here for that purpose. Both plants thrived in their new environments, and spread rapidly without any natural controls to check their expansion. Some invasive species sneak into our environments along with other plants, or even in packing materials, for example, and then by mistake take root and grow.

These invasive plants crowd out native species — and that is where the problems arise. In so doing, they threaten native plant species by spreading throughout an area, taking all available soil, water and sun, which are needed to support the native plants. But these invasive plants do more damage. When an area of formerly diverse native plants is replaced with an aggressive monoculture, the food sources for wildlife are diminished to one source only. While wildlife may indeed like the alien seeds or fruits of the invasive plant, it often is available at one specific time, instead of the range of fruiting or seed-production that a broad selection of native plants offers.

On top of that, the fruits or seeds of invasive plants often do not even provide the proper nutrients native wildlife require. So not only is the food source for wildlife diminished to one period of time, it has been shown to be inferior.

According to the Nature Conservancy: “Invasive species damage the lands and waters that native plants and animals need to survive. They hurt economies and threaten human well-being. The estimated damage from invasive species worldwide totals more than $1.4 trillion – five percent of the global economy.”

Maine’s list of invasive plants is a good guideline for home gardeners, in that it enables them to identify those plants and gives them good reason to begin removing those invasive species from their landscapes. It is important for all gardeners to understand why those plants should be removed. Even though the gardener may not be planting more invasive plants or trees, those plants and trees spread in their landscapes and at the same time are being spread farther afield by a variety of methods — from wind-blown seeds to animals collecting and burying them for winter storage or eating the fruits and then depositing the seeds from those fruits when they are eliminated.

Many of these plants are flowering and can be easily identified with a simple internet search. This is a good time to ferret them out, remove them and replace with native or noninvasive plants. So, what are you waiting for?

Here’s the list, clip it out, save and refer to it often:

Acer ginnala (amur maple)

Acer platanoides (Norway maple)

Aegopodium podagraria (bishop’s weed)

Ailanthus altissima (tree of heaven)

Alliaria petiolate (garlic mustard)

Amorpha fruticosa (false indigo bush)

Ampelopsis glandulosa (porcelain berry)

Artemisia vulgaris (common mugwort)

Berberis thunbergii (Japanese barberry)

Berberis vulgaris (common barberry)

Celastrus orbiculatus (Asiatic bittersweet)

Elaeagnus umbellata (Autumn olive)

Euonymus alatus (winged euonymus)

Euphorbia cyparissas (cypress spurge)

Fallopia baldschuanica (Chinese bindweed)

Fallopia japonica (Japanese knotweed)

Frangula alnus (glossy buckthorn)

Hesperis matronalis (dame’s rocket)

Impatiens glandulifera (ornamental jewelweed)

Iris pseudacorus (yellow iris)

Ligustrum vulgare (common privet)

Lonicera japonica (Japanese honeysuckle)

Lonicera maackii (amur or bush honeysuckle)

Lonicera morrowii (Morrow’s honeysuckle)

Lonicera tatarica (Tatarian honeysuckle)

Lythrum salicaria (purple loosestrife)

Microstegium vimineum (Japanese stilt grass)

Paulownia tomentosa (paulownia, princess tree)

Persicaria perfoliata (mile-a-minute)

Phellodendron amurense (amur cork tree)

Populus alba (white cottonwood)

Robinia pseudoacacia (black locust)

Rosa multiflora (multiflora rose)

Pretty, but invasive, Japanese honeysuckle (Lonicera japonica) is on the list of invasive plants to be avoided and to remove. (Photo by: Lynette L. Walther)
Once used to prevent erosion, multiflora rose has taken over large tracts of land, crowding out native species. It is one of 33 invasive plants targeted by a new state list of plants not only to be avoided, but removed. (Photo by: Lynette L. Walther)
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