Canada Thistle (Cirsium arvense)
How can you not be drawn to the beauty of a fairy-like, pink fringy bloom, especially with a dainty, yellow butterfly atop? Yet the notorious Canada Thistle is a troublesome, invasive weed.
Canada Thistle is a noxious weed in Delaware. This weed with pretty flowers is nothing to play with. It is a huge nightmare for farmers trying to grow a crop or graze their animals. A homeowner or farmer is by law obliged to cut it down and never let it develop flowers.
When something makes it onto the "Official Noxious Weeds" list, it is serious, and we should all do our part to control it. But that label is also a blessing since noxious weeds are eligible for official intervention and removal by government-funded sources.
The less harmful lookalike to the Canada Thistle, Spotted Knapweed, is pictured in the opening photo (sans butterfly). It is also an invasive plant in Delaware, but it is rather easy to eradicate in comparison.
Orange Daylily (Hemerocallis fulva)
Can you believe it? The common Orange Daylily that ordinary folks take home from the roadside and plant in their yards (I know, because I did it, too) is considered invasive. This is due to its free-spreading nature and its reliability: It can be relied upon to come back tenfold next season. This humble relative of prized garden lilies is always happily reproducing itself along the miles and miles of right-of-way in my home state of Delaware. Many young folks just starting out with a country home cannot resist grabbing some and sinking it into their flower gardens. Oops.
Although I haven't tried to remove this common lily from my yard yet, I'm thinking of permanently digging it out. Not so much because the lily goes all over the place—it stays in the general area I where I first planted it many years ago—but because it keeps multiplying, and multiplying, and multiplying, getting thicker and thicker. After its blooming season is over, its huge grassy clump can be unwieldy and a bit unsightly. Yet most local folks like the humble orange lily, or they wouldn't have it in their yards. It is beautiful in its own special way, especially if you like orange.
Asiatic Dayflower (Commelina communis)
Known by names such as whitemouth dayflower or blue dew, Asiatic Dayflower, a distant relative of spiderwort, is invasive. The blue dew type has stunning, dainty, jewel-toned blue blooms that look like faces. So naturally, gardeners like to place it on their properties. Who doesn't want blue flowers?
Sure, it has beautiful blue flowers, but it's not worth the hassle! I speak from experience, but only after I planted it in one of my best flower beds several years ago. Once planted on your property, it will always be there no matter how judiciously you try to remove it. One tiny piece of a stem or root left in the ground will start a rejuvenation, even if you thought you got it all out.
Speaking of stems, this plant is just too stemmy for me.
Even with its blue flowers, a coveted color of many a flower gardener, it requires thoughtful planning as an accent plant. So I am back to digging it up again (because I did not think before I planted it). However, dumping pulled-out dayflower and just piling it in an area for your unwanted plantings will not stop it because it will stretch out roots wherever it lies.
It will always be somewhere on your property. I guess I can live with that. It is pretty, and a bit whimsical for an invasive. But that's just it: It is invasive, meaning it spreads rapidly and monopolizes the planting area in which it is set.
Japanese Wisteria (Wisteria floribunda), Chinese Wisteria (Wisteria sinensis)
Around here, everyone wants a Wisteria vine. Unfortunately, every spring, evidence of Japanese Wisteria and/or Chinese Wisteria run amok is everywhere: its vines with grape-like hanging flower clusters can be seen all along the local roadsides in Delaware as it does its damage strangling and disfiguring anything it can grab.
Then in a few short weeks after Wisteria has lost its lovely blooms for the seaon, everyone forgets about it again since the vine once more blends into its surroundings.
These photos show a mature wisteria vine hugging the trunk of a mature tree. At first, I thought it was a wisteria tree until I got up close. Can you see where the vine emerged from the ground to wrap itself around the tree?
The wide-angle view shows how tree-like a mature wisteria vine can look and how much of a chokehold it has on the poor tree that it is using for support. Wisteria will use anything it can find for support: telephone poles, overhead electric or television cable wires, houses, trees, forests.
A friend of mine has a wisteria vine growing on her fence. She says it takes constant vigilance to keep it in check. Constant. Want some? No, thank you very kindly. I think I'll pass on that offer.
I have a theory about all the wisteria vines I see in the spring that have gotten out of control: They were probably planted by a conscientious person with a green thumb at some point—but that person moved or passed on, leaving a horrific vine that the next person knew nothing about. Consequently, the untended vine took on a life of its own, never to be pruned nor prunable again.
Two Invasives of major concern:
Golden Bamboo (Phyllostachys aurea)
Many local people plant Golden Bamboo on their properties for various reasons since it is quite attractive and exotic. They usually find themselves a few years later with a major problem on their hands that can only be solved by bringing in scientists and government agencies. Bamboo is a grass, a giant grass. What do you do with your normal grass? You mow it. Rigorously, all summer. Because if you didn't, it would overtake your property. And there always seems to be some crab grass mixed in which is impossible to permanently pull out with bare hands because a little rhizome is always left in the ground to regenerate. It's extremely annoying.
Multiply that annoyance times a million and you have Golden Bamboo. Not just annoying, but dangerous and destructive and very much "run amok" in certain places in the U.S., including the Delmarva Peninsula which includes Delaware, Maryland, and Virginia.
A disclaimer is in order: Bamboo is quite useful for the making of many things. It is a beneficial plant when properly cared for and cultivated in its native environment where it is an important part of the economy. But when it is casually placed in a residential area that is worlds away from where it is naturally found, that is an invitation to disaster. And then it is not fun anymore.
The state of Connecticut is currently having trouble controlling bamboo that was originally planted by curious homeowners. The bamboo subsequently sent its long underground rhizomes spiking up under roads, pavements, and residential foundations.
One of our local parks on the Delmarva Peninsula has mature bamboo plantings with surprise rhizomes shooting up all over the park in various and sundry places where you can witness the unpredictability and power of a giant grass firsthand. (The park is now actively taking measures to control the bamboo by removing it and confining it to one specific area.) Good luck with that.
Kudzu (Pueraria montana var. lobata)
Although typically found in the deep south, there is Kudzu in Delaware. The University of Delaware recently conducted controlled studies involving importing weevils from Asia to eat the kudzu. The problem is, the weevils will also eat up a soybean field. Soybeans are a top crop in Delaware.
Kudzu is not an unattractive plant by any means; in years past, it was planted as a shade vine intended to climb up a trellis or porch. I have seen Kudzu in beach towns and found it rather pretty.
Just reading about America's history with Kudzu can be fascinating and entertaining, considering that our government imported it and planted it to help with erosion control many decades ago without really knowing its potential for running amok.
Kudzu is called "The Plant That Ate the South", and a quick "Google Images" search will show you why.
It's amazing to see Google Image pictures of entire buildings and cars covered in Kudzu to the point where you can only guess that there are structures of some sort under the vines. The moral of this story is to think ahead before you plant. Some things that are beautiful and even quite useful in the proper context can get out of hand in a very short time, especially when they come from far-away places across the globe.
Websites and Further Information:
Invasive Plant Species in Delaware by William A. McAvoy, Botanist, Delaware Natural Heritage Program, 2001
Chinese Wisteria link
Japanese Wisteria link
Bamboo removal in Delaware (PDF) March 2012
Bamboo concerns in Connecticut, 2012
Kudzu research, University of Delaware 2008
Photo Credits, Wikimedia Commons:
Canada Thistle with butterfly by Olaf Leillinger, 7-10-2005/Wikimedia Commons
Bamboo leaves by Aktron, 4-17-2010/Wikimedia Commons
Bamboo stalks by Earth100, 9-22-2012/Wikimedia Commons
Kudzu (close range) by Bastique, 5-8-2010, Wikimedia Commons
Kudzu (roadside) by Matt Lavin, 8-1-2003, Wikimedia Commons