Posts Tagged southeastern US invasive plants
It doesn’t look particularly imposing in this picture, but that’s a mountain in the background. I discovered I had no great photos of the majestic Great Smoky Mountains when Wonder Spouse and I returned from our recent vacation in far western North Carolina. All my good shots are of flowers and/or pollinators. Go figure.
Wonder Spouse and I made the trek to higher elevations to celebrate the passage of his recent milestone birthday. For the sake of marital harmony, I shall refrain from identifying the milestone to which I refer. Happy Birthday again, sir!
We enjoyed ourselves immensely, and we met many wonderful folks as we traveled about. However, I found myself often dismayed by what has happened to much of the landscape. From a distance, the mountains are still as beautiful as I remember from childhood visits. On the ground, the story was much different. Almost every single road we traveled was edged by rampant kudzu (Pueraria montana var. lobata) overgrowth. The vines scaled towering rock cuts through mountains, smothering trees, rocks, and shrubs as far back from the road as I could see.
Even in the Nantahala National Forest, kudzu was often the only green plant I could see as we drove along. This was especially horrifying to me as we drove through the Nantahala River Gorge. On the day we were there, the Nantahala River was crowded with kayakers and rafters enjoying the journey downstream through rocky rapids. Perhaps they were too busy dodging boulders to notice that either side of the river was overrun by kudzu — an invasive exotic species originally introduced to the US in the 1930s to control erosion.
The only light moment for me during that drive was a road sign that read “Watch for slow raft buses next ten miles.” Until I saw the old school buses with platforms built on their roofs that held stacks of colorful inflatable rafts, I was mystified.
Invasive exotic plants were mercifully much less evident during our pilgrimage to the Joyce Kilmer Memorial Forest. This preserve protects a forest with 400-year-old trees. Until you’ve stood beneath Tulip Poplars with circumferences more than 20 feet, you cannot begin to imagine what our southeastern forests must have once been like.
Even in early autumn, evidence of mountain wildflowers was everywhere. Tall white plumes of Black Cohosh were still abundant. Stream slopes were adorned with leaves of all the spring wildflowers. They must be quite a sight in April. Deciduous magnolias dotted the hills, along with Cinnamon-bark Clethra. It was quite wonderful to see these native trees where they belong; I hope they eventually look as lovely in my Piedmont landscape where I’ve planted them.
Yellow Jewelweed (Impatiens pallida) was blooming prolifically. I’m not sure I convinced a visitor we met on the trail that this gorgeous yellow wildflower was not an orchid. I tried to explain to him that the orchids native to this habitat don’t bloom this time of year, but I’m not sure he was persuaded.
This wildflower was also abundant at the school where we spent most of our time in the mountains. While Wonder Spouse honed his photography skills, I wandered the large property, where I constantly encountered a depressing number of invasive exotic plant species. This vine was growing on a trail we walked daily to reach the dining hall.
Oriental Bittersweet (Celastrus orbiculatus) was imported as an ornamental for home landscapes. As happens so often, it has escaped into our woodlands. This particular invasive vine is bad in spots in the Piedmont, but not on my property. I hadn’t realized how common an issue it has become in our mountains until I saw it growing here.
During my walks along the grounds of the school we were visiting, I saw many other invasive exotic species throughout the property, including mulitflora rose, privet, Japanese bamboo grass, Princess Tree, Tree of Heaven, and English ivy. All had clearly escaped from former home landscapes. Many of these plants produce fruits beloved by birds, which is how these invaders have spread so insidiously. Others make seeds that are lightweight and travel far via air and water.
The best Web site I know of to learn more about invasive exotic plant species in the mountains of North Carolina is part of the site for the North Carolina Exotic Pest Plants Council. To learn about the mountain invaders and how to control them, go here.
The size and seeming solidity of mountains make it easy to imagine that theirs is an unchanging landscape, where time stands still, or at least moves too slowly for mere humans to notice. My recent visit to the Great Smoky Mountains has dispelled that illusion. The hand of humankind is all too evident. I can’t help wondering how much longer the exquisite ecosystems native to this region can hold out.
Faithful readers of this blog may recall that last month I wrote an entry in which I tried to answer some of the questions from search engines that lead people most frequently to my blog. For example, frequent searches still find my blog while seeking information on tomato ‘Indigo Rose’ and how to tend your garden during record drought and heat waves. Lately, a few other topics have been recurring regularly, so I thought I’d directly address some of them for you today.
First, check out the top photo. We finally got some decent rain last weekend (2.5 magnificent inches), and that moisture rekindled enthusiasm among my vegetables. All but one of my squash plants surrendered to the heat and bugs several weeks ago. But one zucchini ‘Spineless Perfection’ continues to survive and produce fruit against all odds. A close examination of the stem shows clear evidence of Squash Vine Borer intrusion, but this plant has outwitted the bugs by taking advantage of the fresh mulch that Wonder Spouse and I applied to all the paths between the veggie beds. This plant flopped itself over one side of its bed and into the path, and everywhere its stem touches the mulch, it sprouted new roots. Eventually, the borers will overcome this defense, but for now, I’m still picking a few zucchinis every week. I will definitely be growing this variety of zucchini again.
When tomatoes receive a lot of moisture in a short time, sometimes the fruits will split, because they try to expand faster than the skins can stretch. I’m happy to report that the 60 seconds of water my tomatoes were getting every third day during the heat wave/drought, combined with the deep mulch in the paths, prevented my tomatoes from exploding from the recent surge in moisture. As you can see from the photo, all varieties are producing well, and the Carmen and Merlot peppers are also cranking bigtime. Yes, I am cooking down tomatoes into sauce for freezing on a regular basis so as not to waste a single red globe of goodness.
Now, on to a couple of questions.
Princess Tree (Paulownia tomentosa)
In the last month, several searches have found my site searching for a “tree with heart-shaped leaves and seed pods.” Sometimes the search says “giant heart-shaped leaves,” which is why I’m fairly certain these searchers are wondering about Princess Trees.
This non-native, highly invasive tree plagues 25 eastern states in the US. It was introduced deliberately as an ornamental tree, and some lumber companies are now actually growing plantations of these invaders for their lumber, which the Japanese adore. In the spring just as invasive Chinese Wisteria is finishing its blooming period in my area, these trees produce large upright clusters of purple flowers that resemble wisteria flowers from a distance. I suppose some might call the flowers pretty; I call them trouble.
The problem lies with the papery seeds that lurk within the abundant clusters of seed capsules. Experts have determined that one tree produces 20 MILLION seeds in one year. These light-weight seeds float far on wind and water, invading disturbed areas like roadsides and newly logged land. These trees can grow 15 feet in one year, and after they are established, it takes serious perseverance to eradicate them. It can be done. The link above offers instructions and more information on this aggressive invader.
Purple Coneflower (Echinacea purpurea)
Some folks want to know what’s eating the petals of these lovely, tough native wildflowers. The short answer is that any number of bugs may be nibbling on your flowers. In my gardens, where this wildflower thrives on my total neglect, petals do get nibbled. But I have so many that you don’t notice unless you get right on top of them. And I’ve never had a case in which all the petals were devoured. I can always find a plant or two worthy of a photograph.
I’ve also seen questions about whether these flowers multiply, and if they do so every year. In my sandy loam garden soil, my coneflowers multiply vegetatively at least a little every year. From the base of the mother plant, new plants sprout from her roots. When these new plants have a few leaves — usually in late fall — I gently separate them from the mother plant and plant them elsewhere. If I don’t get around to doing this, the baby plants usually manage to grow and flower right where they were born.
Because the central “cones” of the flowers are so showy even in the winter landscape, I don’t cut them off when the flowers fade. I also leave them because the seeds of this native are deemed desirable by goldfinches and several other seed-eating birds. I let the birds devour as much as they want. Inevitably, they scatter some seeds on the ground, at least a few of which sprout to become new plants the following spring. Sometimes, an entire seed head is overlooked by the feathered ones. I can always tell when this happens, because I’ll get a zillion tiny coneflower seedlings sprouting in one spot the next spring. I separate them and transplant them to ensure a continuing supply of these beauties.
Recently, someone found my entry on coneflowers while searching on “my purple coneflower grew a white flower.” Yes, it probably did. In fact named cultivars of white-blooming purple coneflower are sold commercially. ‘White Swan’ is a commonly sold cultivar of this species. If you bought what you thought was a purple-blooming plant from a nursery and it produced white flowers, your seller was careless during propagation. Named cultivars of plants are mostly propagated vegetatively, meaning they grow cuttings from a known desirable plant, or remove offsets from mother plants, as I described above.
But if you grew your coneflowers from seeds, it is entirely possible that one or more of them would produce white flowers. White flowers are a recessive color trait in this species, meaning that two purple coneflowers can produce a white coneflower baby if both carry this recessive color gene, much as two brown-eyed people can produce a blue-eyed child, if both parents carry the recessive gene for blue eyes.
In my gardens, white coneflowers pop up regularly in small numbers, because I do allow the seed heads to complete their life cycles where the plants grow. Personally, I think the white coneflowers contrast nicely with their dominantly purple siblings, adding a little variation to the landscape. I took the following photo of my front garden last year. As you can see, a recessive white-blooming flower grows with its more common purple siblings.
If you bought a named purple-blooming cultivar of purple coneflower from a nursery, you have a right to complain, but if you’ve been letting your coneflowers reproduce on their own, consider the white one a happy addition — a blue-eyed child in a brown-eyed family, if you will.
More answers to your searches in future entries.
Happy gardening to all.
What’s the old saying? Insanity is repeating the same act over and over and expecting different results? Or is that stupidity? Either way, on my five acres of North Carolina Piedmont, my greatest exercise in futility is probably attempting to remove/control Japanese Stiltgrass (Microstegium vimineum). Oh, how I despise this invasive exotic plant species. Let me count the ways.
1. It is ugly and covers everything. As you can see from the above photo, it grows tall and droops over everything, living and inanimate. Even when this annual grass dies with the frost, its straw-like dead remnants bury my landscape in destructive brown yuck. That’s a little pond that fluctuates with the level of the perched water table on my floodplain. I’ve surrounded it with myriad well-adapted wildflowers and native shrubs. But you’d never know it by that photo. It’s one of the areas that I didn’t weed this year. Now my pond environment pays the price.
2. It creates rodent habitat that thwarts predators. As these evil invaders create grassy hummocks over logs, shrubs, and small trees, they create excellent cover for field rats, deer mice, and voles. It’s a tunnel-filled grass metropolis in there. You’d think a rodent population boom would benefit my native predators, especially the Barred Owls and Red-Shouldered Hawks. Alas, no. The grass is so thick and covers so much territory that the rodents can largely conduct their business without ever coming into the open and risking capture.
3. It destroys/alters native plant communities. That’s the edge of my property on the floodplain in the above photo. The green area is where we stop mowing (we mow to reduce tick and snake issues). The hummocks of straw-like material are mounds of Japanese Stiltgrass, which are growing on an area that we used to mow before we figured out it wasn’t technically our land. Behind the Stiltgrass, you can see native floodplain vegetation still trying to fight the onslaught of the invader. It was there undisturbed before the Microstegium took hold. If our floods ever return, that vegetation will likely be overwhelmed.
That’s how the Microstegium got to our property — via floodwaters. Back in the pre-drought decades (how I miss them), our creek usually flooded spectacularly 5-8 times a year. As more and more developments sprouted up nearby, removing forest cover, Japanese Stiltgrass appeared in those developments (probably from seeds off bulldozers and other heavy equipment). This annual produces a lot of seeds, and one of their favorite modes of transport is water. Rainwater runoff carried seeds from those developments into my creek, where floods deposited them on my floodplain.
4. It has killed almost all the wildflowers and ferns that grew along my creek 15 years ago. As you can see in the above photo, the nasty stuff overwhelms everything. Delicate ferns and wildflowers don’t stand a chance.
5. Every object I introduce into my garden is a potential Microstegium support, even though that is never my intention. In the above photo, Japanese Stiltgrass climbs the deer fencing on my north side. I can’t mow right up against the fence because of the way it’s installed. Weedeaters don’t work there either. Hand-pulling is the only option. That’s back-breaking, knee-creaking work. And if you don’t do it before the grass sets seed in mid-summer, what you pull returns a hundred-fold anyway. Did I mention something about an exercise in futility?
6. It wastes enormous amounts of time that Wonder Spouse and I could be using for other things. That mountain is the result of last week’s clean-up of our deer-fence-enclosed north side. It’s about eight feet high and twelve feet wide, and is a mix of fallen branches, leaves, and Japanese Stiltgrass. In areas of our yard where the grass hasn’t invaded, we rake up the leaves, shred them, and use them for vegetable garden mulch. But the leaves in that pile were too heavily tangled with the Stiltgrass to recover. A close-up of the pile demonstrates the problem:
If there’s any good news there, it’s that Mount Brushmore is excellent winter habitat for a variety of birds, racoons, and possums. Air pockets created by piled branches are covered by the thick mass of grass and leaves, creating a thatched roof of sorts that repels rain and insulates against cold.
7-1000. Multiply the above reasons by the number of seeds one plant produces in a season. That’s right. One plant can produce up to 1000 seeds. Contemplating the math is not advised for gardeners with high blood pressure.
When I roamed North Carolina Piedmont woodlands and stream sides as a child and young adult, Japanese Stiltgrass was nowhere to be seen. This invader has transformed/destroyed Piedmont wetlands in just a few short decades.
The deer won’t eat it under any circumstances, but they do enjoy sleeping among the hummocks in winter — instant straw mattresses. I wouldn’t dream of trying to control it with herbicides — not on a wetland, and not with struggling native grasses still present.
One faint hope may be appearing. In Virginia, a fungus has been found to be infecting colonies of Microstegium. The grass seems to be severely impacted by this fungus, and scientists are studying it to determine its origin and whether it can be safely introduced elsewhere to control infestations of Microstegium. All my fingers and toes are crossed on that one. I’ll keep you posted.
Meanwhile, I’ll continue to spend my winters raking dead Japanese Stiltgrass off of plants and structures in the hopes that next growing season I’ll be able to pull the nasty stuff before it sets seed. Oh, did I mention that seeds remain viable in the soil for many years? Yes, sometimes I do wonder why I try to garden at all.
I told you about it here, but I wanted to remind everyone in North Carolina that the week of April 4-10, 2011 has been declared by the Governor of NC to be Invasives Awareness Week. The issue of invasive exotic species is an increasingly serious one throughout the United States, even the world.
And it most certainly is serious in the southeastern United States, especially in the Piedmont region, because so much land is being disturbed as millions of new folks continue to relocate here.
If you live in North Carolina, the North Carolina Exotic Pest Plant Council has set up a Web site about Invasives Awareness Week that lists all the groups across the state holding events to bring attention to this issue during the upcoming weeks. Find an event near you and go learn what you can do to help.
If you live in the southeastern US and you are interested in the health of the fields and forests that surround your homes and communities, I encourage you to educate yourself about this issue. Learn which space invaders are our biggest threats. Learn how to identify and eradicate them from your yards and gardens. The more of us who know about this issue and are willing to do something about it, the more we can all hope our native environments will withstand this exponentially increasing assault on them. A good place to start is the Web site of the Southeast Exotic Pest Plant Council.
And if you’re wondering what invasive species have to do with piedmont gardening, I assure you the two subjects are intimately linked. Gardeners are contributing significantly to the problem by continuing to buy and plant invasive exotic species in their yards and gardens, and to tolerate those already growing there.
But even if your yard is free of invasive species now, it won’t be for long if we don’t take steps to protect surrounding woods and fields from further contamination by non-native space invaders. If our fields and forests continue to be degraded by invaders, much of what we love about the southeast Piedmont will begin to disappear. The first to go will be sensitive wildlife species as their food sources and habitats disappear.
I, for one, don’t want to live in a Piedmont without the summer song of Wood Thrushes in the shrubby shadows, or the caterpillar-devouring help of the myriad warblers that visit during the growing season.
The southeastern Piedmont is a beautiful place. That’s why so many people from other parts of the country and the world continue to move here. I pray that all of us — newcomers and native Piedmonters — will become increasingly wise stewards of these special lands.
Forty-five or so years ago when I roamed the young forests of Alamance County, North Carolina near my home, I never saw Japanese honeysuckle strangling trees. Floodplains and creek banks were covered in moss and wildflowers. Japanese stiltgrass and privet shrubs were nowhere to be found in such places.
The piedmont hills I explored had probably been agricultural fields thirty or forty years earlier. After they were abandoned, healthy piedmont forest began returning as it always had — as it still tries to do today when cleared land is left empty.
But thanks to intentional and accidental human assistance and the efficiency of modern transportation systems, alien species — plants, animals, fungi, and viruses — are moving into areas far from where they evolved. Beyond the reach of the checks and balances of their natal ecosystems, many of these non-native species are rapidly disrupting the native ecosystems they invade. The problem is world-wide and growing exponentially, and it is an issue I believe every piedmont gardener should be aware of.
When I speak to garden clubs about this issue, I am always asked why it’s a problem So what if new species move in — hasn’t that always happened? Isn’t that evolution in action? No, this is not the same for many reasons.
For one, the time scales aren’t the same. Evolution is usually a very slow process, which provides all the components of an ecosystem with time to adapt to changes. But modern transportation and human actions have accelerated the time scale at rates never before encountered by species attempting to adapt to changes in their environment.
And for those of us who love native forests, grasslands, and all our other native ecosystems, invasive non-native species are actively transforming some native environments into biological deserts, where the invading species dominate at the expense of most of the previous inhabitants. We are losing the rich diversity of our native fields and forests that support our wildlife — and us.
At the forefront of this battle to repel alien invaders are the people who manage and protect our national and state parks and other lands designated as worth preserving for their historic importance and/or extraordinary beauty and, often, rare species. Every time gardeners add known alien invasive plants to their landscapes, they are increasing the likelihood that these plants will escape into adjacent natural areas, and eventually, to our special places — our parks and preserves — national treasuries of our nation’s biological assets.
What can piedmont gardeners do? You can identify and eradicate known invasive species from your landscape. And when you go to nurseries and garden centers to buy new plants, always ask if the plant is known to be invasive. If the store clerks don’t know the answer, don’t buy the plant until you’ve researched its invasive potential yourself. And if it is potentially invasive, don’t buy it.
Many non-invasive options exist for your garden. Many on-line resources are available to help you learn more about this subject. And I guarantee you that, wherever you live, nearby conservation organizations are actively dealing with this issue and could use your help. Here are a few links to get you started.