Archive for category Invasive Exotic Species
I’m reasonably certain that’s a Spring Beauty (Claytonia virginica). This early-blooming spring ephemeral wildflower usually starts blooming just a day or two before the American trout-lilies in a moist woodland at the NC Botanical Garden in Chapel Hill. I’ve always thought them to be exquisitely delicate and lovely, and they were on my “Add Someday” list for our five acres of Piedmont chaos. No longer.
Yesterday, Wonder Spouse and I stumbled across two tiny blooming specimens in the middle of our currently moist floodplain. We haven’t mowed there yet, because we’re still picking up fallen limbs from winter storms, which is probably why it managed to push out flowers in time for us to notice. The Spring Beauties at the NC Botanical Garden grow in what becomes deep shade as the floodplain canopy trees above them leaf out. Our volunteers are in a sunnier locale, near a large pine, perhaps enough to give them afternoon summer shade. From this difference, I conclude that Spring Beauties require moisture more than shade.
Our volunteers likely found their way via floodwaters from our little creek, which is only about ten feet from their growing site, in an area that overflows whenever the creek waters escape their banks. We could not be happier to have this native join us: another native to love.
Wonder Spouse and I spent several hours wandering the floodplain/wetland habitats of our yard yesterday, because this is the time of year when their health is demonstrated by the ecological diversity of the beautiful native plants that thrive in the muck. Indeed, there is much to love in a healthy native wetland. There’s also much to worry about: invaders. Non-native, alien species remain the number two threat to healthy native environments world-wide (after outright destruction), and in my yard, we battle invaders constantly.
From Beauties to Bullies
Some battles are nearly hopeless. Japanese Honeysuckle and Japanese Stiltgrass are so aggressively pervasive in our North Carolina woodlands and backyards that the best most of us can do is to try to keep them out of selected areas — a favorite flowerbed perhaps, or a beloved tree, in the case of Japanese Honeysuckle.
Battles Still Worth Fighting
In my wetland/floodplain areas, the invader we are still fighting — so far, successfully <knock wood> is Chinese privet. This evergreen, common hedge shrub of older homes produces blue-purple berries that birds adore. They distribute seeds everywhere, but the privets are most dangerous to floodplain/wetland environments. In some areas in eastern North Carolina, the understory composition of vast acres of wetlands has been completely overtaken by invading privet. Because these non-natives are evergreen, they outcompete wildflowers, shrubs, and tree seedlings for light and other resources. Eastern North Carolina wetlands are becoming biological deserts, consisting of nothing but privet beneath canopy trees. When those trees die, no seedling trees will replace them, because they can’t compete successfully with privet. Eventually, our eastern wetland landscape will consist of miles and miles of nothing but privet.
Plant invaders are overlooked by most folks, because their progress is slower than, say, invading Emerald Ash Borers or Sudden Oak Death. To the untrained eye, green is green. But native animals and plants know how critical the differences are. If you love your southeastern Piedmont landscape, you should know too.
Whenever Wonder Spouse and I walk around our yard, we keep a sharp eye out for Chinese privets (Ligustrum sinense). Seedlings appear constantly, typically beneath trees, where birds deposit the seeds after feasting on privet fruits elsewhere. Yesterday, we spotted several larger shrubs that we had somehow overlooked previously. Greens blend together, and in crowded thicket areas (left for animal nesting habitat), a privet sometimes escapes our notice — for a while. I am especially vigilant in my hunt for this species in my wetland and along the edges of my creek. These areas are most vulnerable to this devastating invader.
While hunting privet yesterday, I was disturbed to discover that some of the Autumn Olives (Elaeagnus umbellata) invading the top of our hill have made it to the floodplain and wetlands. This pernicious invader has taken over many acres of upland environments, such as ridge tops, in my part of the southeastern Piedmont. This species and its close cousins (E. angustifolia and E. pungens) are all non-native shrub species. All are very bad news for the local environment, despite the berries that birds eat with gusto.
Wonder Spouse grabbed his trusty Weed Wrench and went to work on the invading Elaeagnus shrubs, pulling out long-rooted invaders from mucky ground, accompanied by a rather satisfying sucking sound.
Note the flowers just opening on this one:
This was a larger one that put up considerable resistance before Wonder Spouse prevailed:
A New Enemy
And, there’s more bad news for my little patch of Piedmont: Asiatic Hawksbeard (Youngia japonica). This relatively recent annual invader was introduced by the nursery trade. It was probably inevitable, given the number of plants from nurseries that I’ve added over the decades, that this horrifyingly aggressive invader would appear on our property.
To the casual eye, the basal rosette of jagged leaves of Youngia looks quite like that of a Dandelion. But if you look a little more closely, the dangerous differences become evident. It sends up clusters of small yellow flowers on bloom stalks. Dandelions only produce one, much larger yellow flower per stalk. Seeds of Asiatic Hawksbeard look somewhat like those of a Dandelion; they are both attached to white tufts that allow them to float far on breezes. But Hawskbeard seed tufts, like its flowers, are much smaller — and uglier — than those of Dandelions.
I know you’re thinking this is just one more lawn weed, right? Not really. Unlike our common non-native weeds — Dandelion, Henbit, Chickweed, Lambs Quarters — Asiatic Hawksbeard spreads much, much more aggressively. Its basal rosettes are dangerously easy to overlook, and now the experts tell me that they are moving into our dwindling natural areas. In these diminishing patches of native forest, Asiastic Hawksbeard is joining Japanese Stiltgrass, Japanese Honeysuckle, and larger invaders in displacing native wildflowers and other small native plants. Every new invading plant means more competition for food, light, and water for our natives. With no natural predators to slow them down here, their eventual takeover seems a near certainty.
Asiatic Hawksbeard has a taproot similar to that of a Dandelion, and if you don’t get it all when you pull it, the plant will regenerate. Also, you can’t just toss pulled Hawksbeards onto your compost pile. Flowers and even nearly-open flower buds finish their cycle and release seeds into the environment even after they’re pulled. Knowing this, I spent many, many hours last year carefully digging out this new invader from my yard wherever I found it. Every plant went immediately into a trash bag, which I tied and left in the hot sun to fry before adding it to my trash can. Despite my efforts, the Youngia is much more pervasive now that it was last year. And I’m seeing it in all parts of my yard now, whereas, last year, it was confined to only certain areas. The basal rosettes have a distinctive yellow cast, and the leaves are slightly fuzzy. I’ve become quite adept at spotting them. Next winter, whenever we spot one, Wonder Spouse and I are planning to resort to treating them with Round-up. Wonder Spouse and I are ridiculously outnumbered, and this is a war we don’t want to lose.
Reasons to Keep Fighting
And there is so very much to lose. On this Earth Day, let me leave you with a few positive images from our still-healthy wetland, where the wildflowers and other plants are wakening to warming weather with enthusiasm for another growing season.
On this Earth Day — and every day — I will continue to love the diverse and beautiful native species that bless my property. And I will battle non-native invaders as long as I can breathe. Clean water and air can’t exist without the help of healthy native environments — especially wetlands. Do your part today and every day by eradicating invaders in your yard. To learn more about invaders in Southeastern North America, start here.
Autumn is a great time for patrolling your yard/garden. As frost kills formerly lush vegetation, areas hidden by summer are revealed. When I removed a mountain of dead Japanese Stiltgrass from a spot in my north garden yesterday, I discovered a thriving, still-green native blueberry that I planted three years ago. The hideous invasive grass had grown so fast and thickly that I forgot the little blueberry was there. I apologized for the neglect, but fortunately, I don’t think the blueberry was much hindered.
The best surprises yesterday appeared as Wonder Spouse and I walked beside our creek. We’ve been very dry here; we’ll likely be placed into the Abnormally Dry category by the meteorologists next week, unless the rain promised for tomorrow is much more bountiful than predicted. Despite the drought, our creek has more water in it than is usual for such conditions. The water itself barely flows. These signs tell me that beavers are working downstream; their dams prevent the creek water level from dropping. Local inhabitants have noticed the change.
Perched on brown leaves recently discarded by towering Sycamores, we discovered two very bright Green Treefrogs nearly side by side. In Summer’s greenness, I would certainly have passed right by them, but their color contrasted vividly with the browning landscape, making them impossible to miss.
The link above notes these are mostly inhabitants of our state’s coastal plain, but they’ve been creeping west of late. From the recording of their call and previous sightings on rainy summer nights when they climb our windows seeking insects, I know that this species has been part of our wetland for at least 20 years. The frog in the top photo was larger than its companion here:
Both frogs seemed astonished that they were spotted. Perhaps the water level in the creek and the unseasonably warm air made them think they were still camouflaged by Summer’s green cloak. We wished them well, advised them to seek warmer quarters ahead of the latest cold front due tomorrow, and continued upstream.
After only a few steps, as we passed a deeper spot in the creek, several ducks flew up and away in a whoosh of wingbeats. They departed so quickly that we didn’t get a good look, but by their size and general conformation, we suspect they were Mallards. The source I linked to says these ducks are now fairly common throughout my state, and our environment seems to be exactly what they seek this time of year. During Spring, I often see Mallards, Wood Ducks, and some years even Canada Geese. All three species have raised young ones in our wetland.
Right now, the recently arrived beavers are far enough downstream from us that we are gaining the benefits of their presence without any negative consequences. As our forest goes bare for Winter, our trusty binoculars will get much use as we observe increased numbers of wetland-loving wildlife. I confess it is possible for me to lose hours this way.
But beavers are hungry rodents, ever expanding their reach to fell trees for food and dam-building. If they approach too closely, the creek will jump its banks and create a shallow pond across our floodplain. The last time this happened, the water covered an acre and a half, trees were being felled at alarming rates, and those that still stood were dying as the water deprived their roots of oxygen. When this happened, we felt obliged to take steps we did not want to take. I hope circumstances won’t force us there this time.
We made all of these discoveries from one brief Autumn walk with eyes open and ears sharpened. I encourage all my readers to try this. Step outside, into your garden or onto a nature trail. Turn off your electronic devices, remove ear buds. Walk softly through the landscape with your senses tuned for subtle changes. When you really look, you will see.
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.
I call the bloom period of the invasive exotic Chinese Wisteria (Wisteria sinensis) the Purple Plague, because the long, grape-like clusters of blooms are purple, and because the bloom period of this invader visually emphasizes its plague-like effect on our southeastern US woodlands.
I’ll concede that the blooms are not ugly, and many folks like their overpoweringly sweet fragrance, although I’m not a fan. It was the aesthetic appeal of this plant that got it here. Many southerners fell in love with it, draping it over arbors, sides of houses, and training it into artfully shaped waterfall-like forms in their front yards.
If Chinese Wisteria stayed where it was planted, I would not object to its existence in southeastern yards and gardens. But it doesn’t, not by a long shot. Actually, shot is a good word here. You see, the seed pods of this vine are long, bean-like structures. On late autumn days when atmospheric conditions are just right, the pods split open with a resounding crack that sends seeds flying explosively in all directions. I’m told by folks who live near heavily invaded forests that when the pods explode, it sounds like rapid gunfire that goes on and on and on, until all the pods have expended their loads.
Why is this vine considered to be a problem? Take a look at this tangled mess growing along a major road about 5 miles from my house:
Like the evil invader Japanese Honeysuckle (Lonicera japonica), vines of Chinese Wisteria climb over every plant in the forest, creating impenetrable tangles of vegetation that destroy any chance for a healthy ecosystem in such areas.
Chinese Wisteria vines can grow quite large and woody. The extra biomass, especially when vines are leafed out in summer, can add enough weight to burdened trees to make them much more likely to fall or break during wind events created by thunderstorms and hurricanes. During winter ice storms, when one burdened tree falls, those connected to it by this invasive vine are also likely to fall, pulled down by the vines tangling them together.
As with Japanese Honeysuckle, the sprawling masses of tangled vines, trees, and shrubs, create perfect highways for predators like black snakes, raccoons, and other climbers. In such areas, it is vastly easier for these predators to access and devour eggs and nestlings of many of our native songbirds.
In my opinion, there is never a good reason to deliberately introduce invasive Chinese Wisteria into a landscape. It will not — not ever — remain only where you plant it. It will — without question — escape into nearby woodlands, where it will destroy the integrity, beauty, and health of these small forests that are essential to native wildlife and plants.
And there’s a native alternative to this invader: American Wisteria (Wisteria frutescens). It is not as flamboyantly showy as the Chinese invader, but it performs the same functions — covering arbors, for example, just as beautifully with similar flower clusters. Most importantly, our native Wisteria vine does not escape and destroy our forests — reason enough to plant it instead, if you ask me.
I will freely admit that Chinese Wisteria is not the most damaging invasive exotic plant species in my region of the country. But it’s blooming and very visible right now, so I think it serves as perfect symbol for North Carolina’s second annual observance of Invasive Species Awareness Week, which runs from April 1-7 this year. Many conservation-related organizations plan activities during this week that highlight this issue. The site links you to a calendar of events occurring throughout the state this week.
Many botanists and ecologists believe that invasive species represent one of the top two threats to our native ecosystems. The other threat is habitat destruction due to land clearing. These two issues are related. As more land is cleared, smaller tracts of native forest remain. These smaller tracts are much more easily overtaken and destroyed by exotic invasive species.
If you live and garden in North Carolina, I ask that you take a few moments to visit this link to the Web site of the North Carolina Exotic Pest Plant Council to learn more about invasive species in our state.
If you live in a different state in the southeastern United States, visit this link to the Southeast Exotic Pest Plant Council. The home page includes links to all the member state organizations, so you can find out what they’re doing about invaders in your state.
As a life-long gardener in the Piedmont region of North Carolina, I can personally attest to the transformation of my native woodlands by invasive exotic plants. When I was child roaming Piedmont woodlands in the 1960s, Japanese Honeysuckle was not strangling the trees. Autumn Olive (Elaeagnus umbellata) and Japanese Stiltgrass didn’t overwhelm my beautiful woodlands until a decade or two ago. Same for Chinese Privet (Ligustrum sinense). The invaders are coming faster now and establishing themselves much more quickly.
Anyone who cares about the long-term health of our native ecosystems should be deeply worried. I know I am. Please educate yourself about these invaders, learn about the many lovely native plant alternatives to the dangerous species.
Much good information is out there. Besides the Southeast Exotic Pest Plant Council site, try the information-packed Web site of the North Carolina Botanical Garden. Here’s a link to their list of exotic invasive plants to avoid. And here’s a link to the page where they offer suggestions for native plant alternatives.
With just a bit of effort, your garden and yard can become part of the solution to this growing problem. Please consider joining me in this battle against alien invaders. Together we can fight the Purple Plague, and restore a healthy balance to our native landscapes.