eGarden © 2004 Ed Mues

The Attack of the "Killer Plants"

A few years ago, my wife Diane and I were out for a drive. It was late summer. Both roadside and at some greater distances we saw fluffy white clusters of blooms held eight feet or more above the ground. Simply beautiful! Diane commented how nice they would look as a backdrop where our field meets the woods. She was ready to dig some up from an abandoned area near our home. "Hold on", I said. "Have you noticed that right down the road from us, those neighbors have been trying for years to rid themselves of that plant from both sides of the road?"

This plant is a foreign invader, or, if you like, an exotic species from outside our country. It was introduced and escaped from cultivation. It reproduces (as most weeds do) very successfully, both from an extensive root system, and, to a lesser degree from seeds. It is known as Japanese Knotweed or Japanese Bamboo. It is not related to bamboo, but shares the hollow stem, sections, and vigorous spreading growth that probably helped it earn the nickname. Botanically it is Polygonum cuspidatum. (Literally, "many angled spear-pointed", a description of its growth habit above ground.) It is related to the very common smartweed, lady's thumb, and wild buckwheat. To say it's successful is an understatement. It is a major problem. I'll go into this in greater depth in a little bit. But, first, a related account.

For several summers while working at Cornell Cooperative Extension in Liberty, calls would come in from summer visitors asking, in essence, if it was okay to dig up some of the beautiful purple flowering plants seen along the way in wet spots. After the usual cautions about private property, state lands, etc., I would tell them that it was not okay to dig them and transplant them. The reason is the same as for the Japanese Knotweed. Purple loosestrife, too, is a foreign invader that easily escapes cultivation. Just as successful a weed as the above-mentioned, it is a prolific producer of seeds that are easily moved about by a variety of animals, wind, vehicles, water, and muddy shoes or boots. Don't plant even one! A single purple loosestrife plant produces more than two million seeds in one season.

As promised, there are more profound reasons behind discouraging the rapid spread of some weeds. Not unlike their insect counterparts, such as Gypsy moths and Japanese beetles, botanical invaders from abroad pose enormous threats to America's native life, plant as well as animal. As native plants are crowded out, native wildlife loses preferred food sources and nesting areas. As the aliens spread, they hybridize with natives, support other non-native plants, animals and diseases, ultimately altering entire ecosystems. The problem becomes self-perpetuating because the aliens have few, or, more frequently, none of the controls of their country of origin -- no predators, pests or other organisms to limit their successful spread.

The old definition of a "weed" -- a plant growing where it's not wanted -- needs to be seriously updated. I suggest something like any plant having a negative impact, economic or otherwise, on the health of another living ecosystem, be it human, animal, botanical or environmental. This influence can be far reaching. It might include food crops, forage crops, landscapes, aesthetics of open spaces, gardens, nurseries, golf courses. The issue is a double edged sword, however. A red maple tree is a handsome element in a landscape. But, the hundreds upon hundreds of seedlings that sprout in nearby landscapes as well as flower and vegetable gardens, these are certain to be regarded as weeds. The same is true for timothy and orchard grass, both valuable forage crops. These grasses easily get established, however, in orchards and low till vegetable farms, becoming weed pests to be eliminated.

Thousands of plants growing here are not native to North America. Luckily, for now at least, not all are problematic. Federal agencies have named nearly 1400 as exotic and pests. Three hundred of these have been positively classified as invasive plants. Curiously, but not too surprisingly, it is now believed that nearly half were introduced to the U.S. to enhance and beautify gardens and landscapes. Of these, ninety-four are officially categorized as Federal Noxious Weeds that infest (are you ready for this?) in the neighborhood of 100 million acres coast to coast. Plants on this list include all types: trees, shrubs, annuals, perennials, grasses, aquatics, and vines.

Some are startling surprises. Some were recommended by the Federal Government and distributed by their agencies. Multiflora rose, native to Japan, Korea, and eastern China, was promoted by the U.S. Soil Conservation Service in the 1930s. At the time it was recommended to stem soil erosion and serve as a living fence for livestock. Soon after, it was touted as a valuable source of wildlife cover and songbird food. We all make mistakes. The many problems with the plant didn't become apparent until years later. It still prowls about our lands in fields and meadows and occasionally in cultivated landscapes. Free rooted cuttings were once handed out. Millions of dollars have been spent trying to eradicate Multiflora rose since then.

We all make mistakes. I contemplated moving some English Ivy from Long Island to the shaded floor of my evergreen wood lot. Two years later, English Ivy was listed as a noxious weed in Oregon and Washington. Whew! I might have made a big one. It gave me pause for thought. Plant lovers need to be more aware and more vigilant. A recent headline from the Oregon Department of Agriculture: "State Weed Board takes action on invasive plant that can harm reforestation efforts. Popular butterfly bush added to noxious weed list." Feb. 25, 2004. "Wow!", I thought. "We're all only human. We all make mistakes."

The State of Connecticut just passed an "Act Concerning the Ban on Invasive Plants". In part it reads " ... no person shall import, move, sell, purchase, possess, cultivate or distribute any of the following plants...". More than eighty plants are named including forget-me-not, black locust, autumn olive (two years ago, sold and recommended by some of our government agencies) and fig buttercup among the rest. Another list from U.S. Fish and Wildlife Service lists 49 plant Invaders. Prof. Larry Kuhns from Penn State's College of Agricultural Sciences as early as 1999 suggested that "... invasive plants may be the top environmental issue of the 21st century."

These botanical interlopers extract enormous tolls, to the tune of many billions of dollars annually. The agriculture and horticulture industries, in addition to the real money lost, also lose from large investments of time and effort, a secondary block of billions of dollars. Our water quality and air quality are impacted, as well as our fish and other wildlife. Imagine the money that could be saved, if only from the point of view of those with pollen allergies. I guesstimate non-native plants produce tens of millions of tons of pollen each year. Many of these aliens are responsible for poisoning people and livestock.

A few years ago, an elderly Italian gentleman, his name escapes me, brought a plant to me for identification. He claimed he'd been cultivating and eating it for years. What do you think it was? The ubiquitous, common as dirt, garlic mustard, Alliaria petiolata. This extremely successful intruder from Europe continues to spread and poses a serious threat to any native wildflowers in its range.

So, what is one to do if one seeks to enter the fray?

First, I would think of getting a good book for identifying weeds, natives and exotics. A field guide would be great. You could slip a piece or two of paper in it, bring along a pen or pencil and go for a walk. Your notes would be extremely helpful when you returned home.
Pull weeds growing in the wrong place when they're young (easy), but surely, before they flower and produce seeds (more difficult).
Mulch, mulch, mulch.
Start a local eradication program. Get to know one plant really well this season, and next season begin to wipe it out early and with regular follow-up. Try garlic mustard.
Put in native plants whenever possible. Hundreds of species are available, and you'll see the return of native birds and butterflies as a bonus.
Never introduce a plant from the wild unless you know its identity, growth habits, and origins.
If you purchase plants regularly, do a bit of extra homework.

There are many non-native plants that are attractive. Hollyhocks are from Europe and Asia. They seed readily and spread vigorously. The herbicide Round-up is often used to control them. In a field they are wonderful to see, but at what cost to native wildflowers and animal species? A field of wild daisies? Twenty-six species of Leucanthemum are from Europe and temperate Asia. They are all here. They are beautiful to see 'en masse'. But, at what cost?

In a future article, I will address engaging in the battle in a more serious way. Chemical, botanical, organic, not necessarily in that order. And, there is still the hotly debated native vs. exotic question. It's fraught with controversy. I'll do my best to report.

From The Garden of Ed. Submitted for publication in The Towne Crier on July 14, 2004

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