New rules for wild invasives

By Tom Seymour | Feb 16, 2017
Photo by: Tom Seymour Dame's rocket has four petals, while phlox, which it closely resembles, has five.

The Maine Department of Agriculture, Conservation and Forestry announces a list of 33 plants that it deems invasive, likely invasive and potentially invasive. As of Dec. 31, it will be illegal to Import, export, buy, sell or propagate any of these plants.

The intent of this new law is based upon admirable intentions. A problem arises, though, with a select few of these plants that are unjustly blamed for a rampant takeover of our woods, fields and streamsides.

For instance, let’s consider dame’s rocket, Hesperis matronalis. A biennial, dame’s rocket is often confused with garden phlox because it is of a similar stature and the flowers are also similar, with one big exception. Dame’s rocket has four rays, or petals, and phlox has five.

Dame’s rocket was awarded the invasive rating, meaning it will spread quickly at every opportunity. But is that really true? The problem with wild invasive plants is that truly invasive ones can overrun habitat, overpowering native species. Given that, I have yet to see any place overrun with dame’s rocket to the extent that native plants were endangered.

Dame’s rocket grows in both rich, fertile soils (think garden soil, or even lawns) and poor, gravelly soils. A good place to go in June to see blooming dame’s rocket is along railroad tracks. There, rocket grows alongside the tracks, imparting not only a wash of white, pink and purple color, but also a heady, sweet fragrance. Rarely does rocket venture far from the railroad bed.

I often spy rocket growing on the edge of someone’s lawn, sometimes near the garden area. Those plants have, no doubt, resided in the same place for many generations, reseeding themselves through the years. As such, dame’s rocket adds a pleasant, if seasonal, dimension to its surroundings. It’s hard to imagine how anyone would or could find fault with dame’s rocket.

Having a four-petaled flower, dame’s rocket belongs in the mustard family, as evidenced by the somewhat spicy flavor of the young leaves when simmered in water.

But nonetheless, dame’s rocket has been given a death sentence and there’s not much anyone can do about it. It does seem sad that a homeowner who wishes to spread some rocket seeds in order to enjoy these beautiful flowers cannot legally do so. Lucky for me, I got dame’s rocket growing around my place in time to avoid legal penalties.

Japanese knotweed

Homeowners usually refer to this plant as “bamboo,” which it superficially resembles because of the nodes and internodes on its stalk. Knotweed, Polygonum cuspidatum, grows in thick stands. The old stalks (9 or 10 feet tall) persist throughout the winter and well into the following season.

Japanese knotweed was originally brought to this country during the Victorian era as a handsome horticultural specimen. It was the greenish-white flowers, tiny individually, but attractive because they are arranged on a long, wispy stem, that Victorian people so admired.

The current war against knotweed has long been a sticking point with me. Deemed a harsh, vigorous invader, Japanese knotweed is nowhere near as bad as it is portrayed. It all depends upon where it grows and how we treat it.

Knotweed happily grows on nutrient-poor soil as well as rich soil. When left alone, Japanese knotweed does not usually spread very fast. I know some homeowners will disagree with that statement, but nonetheless, knotweed isn’t as bad as it is portrayed.

Consider the ancient knotweed plants found near old foundations and such. These stands often encompass an area of 20 or 30 feet in circumference. But these plants were put there 120 or more years ago. It’s little wonder that the stand has expanded.

As far as just jumping around from one place to another, the worst of these situations are usually examples of human interference. Knotweed readily propagates itself through tissue culture. Just dig up a little bit and that little bit will quickly grow to a full-size, shrub-like plant. But for that to happen it must first get dug up. And therein lies the rub.

We have all seen expansive stands of knotweed growing in roadside ditches. Most of these came from just a tiny plot of knotweed that would never have escaped its bounds on its own. But when a town or city decides to dig or even freshen roadside ditches, the excavator inadvertently spreads knotweed tissue and, in effect, plants it where it didn’t grow before.

So the real culprit concerning the spread of Japanese knotweed is not the knotweed itself, but rather, the municipalities.

I’ll never convince anyone that knotweed isn’t as bad as it is touted to be. But perhaps my words can take some of the edge off the rhetoric used to demean it.

By the way, when young, 8- to 12-inch knotweed shoots are simmered in water like asparagus, they are delicious. And stewed knotweed closely resembles stewed rhubarb. I sometimes make a delightfully fruity-tasting knotweed chutney. So much for this poor, condemned plant. And as per laws regulating knotweed, it should be illegal for municipalities to spread it during ditch work. And, of course, homeowners never purposely propagate knotweed.

Bishop’s weed

Here’s a pop quiz. What is bishop’s weed? It’s kind of an odd common name for Aegopodium podagraria, otherwise known as goutweed. Goutweed, in various forms, has long been used as a border plant in perennial gardens. And since it, like Japanese knotweed, spreads quickly by tissue culture, it has greatly spread its range by virtue of the ditch-digger’s dozer blade.

So here is another plant that has fallen from grace. My own bishop’s weed has a hard time growing, given the gravelly soil where it was planted. But if I decided to revamp my ground, bishop’s weed, or goutweed, would probably have a better chance to survive and prosper.

But is bishop’s weed as bad as it is now rated? Well, for starters, it is listed as “likely invasive.” That alone should serve as a clue that bishop’s weed isn’t going to take over the state of Maine anytime soon.

Mugwort

Common mugwort, Artemesia vulgaris, grows in roadside gravel and is now listed, and condemned, as likely invasive. Being an artemesia, mugwort is a wild cousin of wormwood, Artemesia absinthium. Wormwood, a bitter herb popular in biblical times, is grown in the perennial garden where its light-green foliage makes a gentle contrast with more colorful plants.

Mugwort, an alien invader, as so many wild plants are, has firmly established itself in rough ground, notably roadsides. Mugwort, like so many other unfairly-rated wild plants, is listed as likely invasive, which brings to mind the question, “Is it or isn’t it?” I give mugwort the benefit of the doubt.

Mugwort, with its pungent, spicy scent, is commonly seen along late-summer roadsides. Its leaves are dried and used as a tea to combat cold and flu symptoms. It is quite effective in this respect.

Fortunately, those who view mugwort as an innocuous, beneficial herb rather than as something to be despised will probably always have a ready source of this healing herb along the rough ground of roadsides and right-of-ways.

Tom’s tips

I recommend that before accepting the now-common view that the four plants mentioned in this column are our enemies, readers should take a second look. The adventuresome might wish to try some of the listed uses. In the end, dame’s rocket, Japanese knotweed, goutweed and mugwort may become cherished friends, rather than despised enemies.

Mugwort is a common roadside medicinal plant. (Photo by: Tom Seymour)
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