16. THE INVASIVES ARE HERE
The invasives are not only coming, there already here and spreading throughout the landscape. Here are some of the top invasives. These are the ones that take place outside your garden on the edges of woods, roadways, pastures, next to streams, in wetlands and elsewhere in nature. They include Common Reed, Garlic Mustard, Honeysuckle, Giant Hogweed, Japanese Barberry, Buckthorn, Japanese Knotweed, Purple Loosestrife, Wild Chervil, Multi flora Rose, Wild Parsnip and Poison Ivy.- NOT IN THIS ORDER *See information on the most common invasive - Gout Weed – found in perennial gardens.
Non-native plant species pose a significant threat to the natural ecosystems of the United States. Many of these invasive plants are escapees from gardens and landscapes where they were originally planted. Purchased at local nurseries, wholesale suppliers and elsewhere, these plants have the potential of taking over large areas, affecting native plants and animals and negatively changing the ecosystem. In recent years, an increase in travel and international trade has rapidly introduced many new non-native species to the United States.
Plants with the highest invasive potential are prolific seeders and vigorous growers which have the ability to adapt well to a variety of conditions. Native species have not evolved alongside these plants and have trouble competing. With few predators and little competition for resources, these new plants can displace native flora, reducing plant diversity until a landscape is no longer able to support longstanding native plant, animal, and insect communities
Purple Loosestrife (Lythrum salicaria) was introduced to the United States in the early 1800s for ornamental and medicinal uses. Now growing invasively in most states, purple loosestrife can become the dominant plant species in wetlands. One plant can produce as many as 2 million wind-dispersed seeds per year and underground stems grow at a rate of 1 foot per year.
Native Alternatives: Blazing star (Liatris spicata), American blue vervain (Verbena hastate) and New York ironweed (Vernonia noveboracensis.
-Purple Loosestrife is considered such a noxious weed in many states that it is illegal to purchase and plant. This non-native plant produces a bounty of seeds, many of which germinate in waterways, marshes and bogs, taking over native vegetation and over runs its competitors in wetland areas.
Loosestrife was introduced in the European ship ballasts. It's used as a medicinal herb for the treatment of diarrhea, dysentery, bleeding, wounds, ulcers and sores. It originated from the temperate regions of Europe and Asia. Control methods include hand pulling, cutting, burning, and herbicide treatment. Most of these methods will kill the plants but not the large seed heads that allow rapid reestablishment. That's why breaking off the flower heads before they go to seed is helpful. Put the discarded seeds into plastic bags to decompose. In Vermont, there has been some success with two leaf eating beetles. I haven't noticed as much purple loosestrife as I used too. What is your experience?
One herbalist uses the loosestrife flowers mixed with honey for an herbal remedy. The flowers appeal to bees and can be a valuable source of nectar. Todd Hardy, a Vermont beekeeper for over 50 years, said that when there are droughts, purple loosestrife is one of few plants whose nectar is available. Hardy said that he has removed the stalks after the bees visit and dries the leaves and flowers to mix with alcohol and propolis to make a tincture.
-Japanese Knotweed - This noxious weed is non-native and poses a great threat to the environment. It came to America from Japan. Knotweed can be harvested when it’s young and tender for your dinner plate.
It has a stronger more astringent taste than rhubarb. So you guessed it, the shoots need lots of sweetening. The culinary use of knotweed could help with its control because the young shoots are harvested in spring and used like asparagus. The worst that might happen would be for it to spread in the harvest. The excess should be disposed of where it cannot spread.
Knotweed has an extensive underground horizontal rhizome system that can extend up to 60 feet. When it’s disturbed, it sends up new shoots, as when Hurricane Irene hit Vermont with a vengeance. In the fast-moving streams, little bits of the stem germinated into new plants with ease, so if you are going to disturb it by cutting/removing it for three years, you gotta get it all and then pray. Whatever you do, don't throw it onto a compost heap.
Knotweed is a bamboo like member but not a true bamboo of the Smartweed family. It's a native of Japan. The plant can grow to 12 feet high. Japanese Knotweed was introduced as an ornamental into the United States in the late 1800s, and has naturalized throughout eastern North America along the coastal area of Oregon and Washington and in much of the Midwest.
The most promising method of control may be the repeated cuttings of these polygonum stalks up to three or four cuts a year or more. This many cuts along with stream bank restoration may help. Chemicals (glyphosate Roundup) and machinery can also be used, but I don't recommend it as Roundup is connected to cancer in animals and recent research shows a connection to humans. Digging up the plant is not recommended as it will likely fragment the rhizomes and lead to further spreading. I'm not sure there is an easy answer. The key is to counter rhizome production with continuous cuttings.
It needs cutting to reduce its vigor and eventually wipe it out in a specific location. The Vermont Nature Conservancy suggests piling the cut stems under a tarp where it can thoroughly rot.
Knotweed thrived in the aftermath of Hurricane Irene (late August 2010), because it spreads quickly in disturbed soils. The floodwaters from the tropical storm spread portions of the stems and woody rhizomes on riverbanks, floodplains and roadsides, choking out native plants with deeper roots, degrading fish habitats, birds, and insects and weakening stream banks, which led to erosion and flood damage. Efforts are underway to restore those bare banks with native trees and shrubs that will shade out knotweed.
*Check out recipes for knotweed in Euell Gibbon’s famous book, "Stalking the Wild Asparagus." Why not try out stir fried burdock or knotweed chutney?
-Japanese Barberry (Berberis thunbergii) Origin: Japan
Arrival: Japanese barberry was introduced to the United States in the 1800s as an ornamental. Seeds of Japanese barberry were sent from Russia to the Arnold Arboretum in 1875 as an alternative to European barberry (Berberis vulgaris), which had fallen out of favor as it was a host to Black Rust Stem—a serious fungus effecting cereal crops.
Impact: The shrub has the ability to grow in deep shade and is particularly detrimental to forest lands in the Northeast. The heavily fruiting plant forms dense thicket, crowding out native plants, and its seeds are easily spread by birds.
Native Alternatives: Shrubby St. John’s wort (Hypericum prolificum) and winterberry (Ilex verticillata)
The Japanese barberry is not the traditional New England barberry often seen in abandoned pastures. It's making its presence known throughout New England. It was brought in by nurseries as a landscape plant and is thriving in our gardens as well as every other place where it can get a foothold. Again it's the birds that eat the berries and drop to the seeds to the ground in their dung.
-Norway Maple (Acer platanoides) Origin: Europe
The plant explorer John Bartram first introduced the Norway maple to the United States from England in 1756. The widely adaptable tree quickly became popular and was planted in towns as a shade tree and in rural communities. The Norway maple displaces native trees and has the potential to dominate a landscape in both the Northeast and Northwest. It displaces native maples like the sugar maple and its dense canopy shades out wildflowers.
Native Alternatives: Sugar maple (Acer saccharum) and red maple (Acer rubrum)
-Invasive Trumpet Vines and Japanese Honeysuckle
Gardeners may be plagued by these two overly aggressive or hard-to-eradicate flowering non-native invasive vines. These pesky plants in the United States are the trumpet vine (Campsis) and the Japanese honeysuckle (Lonicera japonica), a noxious weedy species.
*Common or colloquial names for these two groups of flowering vines can cause confusion. Names like trumpet vine, trumpet creeper, trumpet honeysuckle and honeysuckle vine may all refer to the same plant in a region or carry specific association to only one plant. Please be advised – they are not the Climbing Honeysuckle (Lonicera sempervirens) described earlier.
Trumpet vines or trumpet creeper refer to plants in the genus Campsis. In the United States, Campsis radicans widely grows. It grows in rounded clusters on stem tips. They produce funnel-like flowers lacking long anthers.
Trumpet vines grow fast. The yellow varieties are less aggressive than the traditional orange ones. I once grew an orange variety and it attempted to take over my house by literally digging with its claws into the wood, so please plant the vine away from your home on a heavy-duty fence. It took me a couple years to get rid of the Trumpet Vine and it still shows its head now then. I just keep pulling it out. It’s no longer on the cedar shingles on my home. The “Chuckster” just said, “Yeh sure.”
Lonicera japonica is a woody Japanese honeysuckle perennial, evergreen to semi-evergreen vine that can be found either trailing or climbing to over 80 ft. in length. Flowering occurs from April to July, when showy, fragrant, tubular, whitish-pink flowers develop in the axils of the leaves. The flowers turn cream-yellow as they age.
Invasive Honeysuckle Shrub - Morrow's honeysuckle (Lonicera morrowii) is a deciduous honeysuckle native to Japan, Korea, and Northeast China. It is a shrub, reaching a height of 2-2.5 m, with oblong leaves 4–6 cm long. It leaf’s out quite early in the spring, and in North America is commonly the first deciduous shrub with foliage in March. The flowers are white to pale yellow, and the fruit is a dark red berry containing numerous seeds. The berries, while eaten frequently by birds, are considered poisonous to humans. It is colloquially called "bush honeysuckle" in the United States, and is considered a highly invasive species
over the northeastern third of the United States.
Morrow's honeysuckle thrives at the edges of forests, roads, or other natural or man-made barriers, but is not limited to them, and is found in both mature and disturbed forests. In some areas, Morrow's honeysuckle is the dominant plant species, especially in areas of disturbed ecological succession. It is suspected that Lonicera morrowii is allelopathic, and may capitalize on disturbed ecological succession by establishing itself and then preventing the growth of plants underneath it. It is so invasive that it can take over forests if not contained, which is very hard to do. Dense growth of invasive honeysuckle covering vegetation can gradually kill plants by blocking sunlight from reaching their leaves. Vigorous root competition also helps these bush honeysuckles spread and displace neighboring native vegetation.
*A rare low shrub called Canada fly honeysuckle only grows one to three feet is usually found in wet woodlands. Lonicera villosa
mountain honeysuckle is native to northern North America, and has oval leaves and yellow flowers. It can be propagated from seeds or cuttings, and grows best in dappled shade of moist, cool sectors of northern gardens.
The twining vines, such as honeysuckle, climb by winding their stems around any available support. These two types - twining and tendrils--are suited to climbing on wires, trellises, or arbors but can be grown on flat surfaces if proper supports are provided for them.
The climbing vines are better adapted to climbing on even, vertical surfaces. These fall into two types. One, such as the Japanese creeper (Parthenocissus tricuspidata), climbs by means of tendrils with disk-like adhesive tips that attach themselves firmly to any surface, even glass.
The other type climbs by means of small aerial roots at intervals along the stems. These dig into the crevices of any rough-textured surface, such as brick, and cling tightly. When allowed to trail on the ground or climb in the joints of a dry-laid stone wall, they will root and form new plants.
Clinging vines look nice on brick buildings, but keep in mind that the vines can damage masonry and mortar. It's also a good idea not to grow them along the walls of frame buildings as their method of climbing might damage the wood of the structure. They cling so closely to the wall that dampness is likely to collect under them and rot the wood.
If, however, vines seem desirable in certain cases, the trellis on which they are trained should be far enough from the siding to allow air to circulate freely behind the vine. The trellis should be removable so that it may be laid flat on the ground to permit painting or cleaning of the siding without damaging the vine.
-Japanese Honeysuckle (Lonicera japonica) Origin: Eastern Asia Arrival: One of many invasive varieties of honeysuckle in the United States, Japanese honeysuckle was brought to Long Island, NY, in 1806 for ornamental use and erosion control.
Impact: The plant has become prolific throughout much of the East Coast as it adapts to a wide range of conditions. Japanese honeysuckle is an aggressive vine that smothers, shades and girdles other competing vegetation. Many of the birds eat the fruit of this plant, thereby spreading the honeysuckle’s seeds.
Native Alternatives: Trumpet creeper (Campsis radicans) and coral honeysuckle (Lonicera sempervirens)Honeysuckle – Japanese honeysuckle is another invasive, which is having a heyday. It grows along roadsides, the edges of woods and abandoned pastures. Since honeysuckle produces lots of fruit and seeds, the birds again are spreading the bad news through elimination. Not all honeysuckles are invasive. You can tell if the honeysuckle you've identified is invasive by cutting the stem. If it's hollow, it's invasive.
-English Ivy – The introduction of English ivy dates back to the early 1700s when European colonists imported the plant as an easy-to-grow evergreen groundcover.
Impact: The planting and sale of English ivy continues in the United States even though it is one on the worst-spread invasive plants in the country due to its ability to handle widespread conditions, particularly on the east and west coasts. English ivy is an aggressive-spreading vine which can slowly kill trees by restricting light. It spreads by vegetative reproduction and by seed, which are consumed and spread by birds.
Native Alternatives: Creeping mint (Meehania cordata), Allegheny spurge (Pachysandra procumbens) and creeping phlox (Phlox stolonifera)
-Kudzu (Pueraria montana var. lobata)
Origin: China, Japan and the Pacific islands
Arrival: Japan introduced Kudzu to the U.S. at the Philadelphia Centennial Exposition in 1876. It was first promoted as an ornamental plant and later as a forage crop in the Southeast. One million acres of Kudzu were planted in the 1930s and 1940s by the Soil Conservation Service to reduce soil erosion on deforested lands. It was not until the 1950s that it was recognized as an invasive.
Impact: Once established, Kudzu grows at a rate of up to one foot a day and 60 feet annually. This vigorous vine takes over areas in the Southeast by smothering plants and kills trees by adding immense weight and girdling or toppling them.
-Garlic Mustard - Garlic Mustard is a biennial herbaceous plant with single stems and white flowers. Its white taproot smells like horseradish. Its numerous leaves and stems smell like garlic when crushed. You might say it's a very unwelcome guest in our gardens and forests, as it produces chemicals with anti-fungal properties.
Unfortunately, it sometimes spreads into gardens.
Garlic Mustard is native to Eurasia and was introduced to North America in the 19th century as a culinary herb. It can produce allelochemicals that suppress mycorrhizal fungi in the soil and therefore can disrupt a healthy relationship between hardwood tree seedlings and soil fungi, with results that can be disastrous for a forest. (Mycorrhizal fungi provide beneficial relationships with the roots of young forest tree seedlings and garden plants and help with the uptake of water and nutrients. They do this with an elaborate network of filaments throughout the soil by connecting to the fine feeder roots of trees and plants.)
The leaves contain natural freezing elements, which allows the plants to overwinter in Vermont. It is easy to see in April and May with its white flowers. Garlic mustard was first planted on Long Island in 1868 as an edible garden plant.
The flavor of its leaves are true to its name as the young tender leaves can be used as a tangy salad green or in pesto. The Richmond, Vermont Floodplain Forest Restoration Project issued a page of recipes titled, "If You Can't Beat It, Eat It." Recipes included garlic mustard pesto, baked knotweed, garlic mustard and spinach ravioli, and garlic mustard cornbread. On the Rise Bakery in Richmond serves up garlic mustard pesto. I think we're going to need to make tons of garlic mustard pesto if we're going to combat this nasty weed, but it will take more than that to remove this harmful invasive.
In 2006, garlic mustard was identified as a noxious weed. Once it comes into a new area, it spreads and becomes the dominant understory species in woodland, fields and flood plain environments where eradication is difficult. It can take over native herbaceous plants and alter the native insect population.
Pull the plants in the spring before they flower grasping them at the stem base to get the full root out. Put all the plants in a plastic bag and let them decompose at the dump. Do not compost as the plant fragments can re sprout. In my neighborhood, garlic mustard has taken off invading many niches and corners. It shows up anew in places you've never seen before.
-The Giant or Common Reed (Phragmites) - The Common Reed is found everywhere. Paleo ecological studies in Connecticut have found 3,000-year-old fragments of Phragmites.
Cutting the reeds can control this invasive, but they need to be cut at the right time and for a number of years. The plants should be cut before the end of July, when most food reserves are in the aerial portion of the plant. Glyphosate herbicide has been used along with prescribed burns and the re-establishment of native plants. There has also been some success with the use of black plastic. Healthy, stable, natural plant communities are the best defense against the invasion and spread of the Common Reed.
-Common Buckthorn; Glossy and Tall Hedge Buckthorn
Birds love the berries of the buckthorns. In fact, they do such a good job of spreading the dark seeds in the fall with their droppings that buckthorn has become a terrible weed species, running wild and taking over many natural wooded areas. It can grow up to 15 feet in the northern woods and is considered a shrub like tree. It came into its own after the great ice storm of 1998 when many of the woodlands were decimated. This provided an opportunity for Buckthorn to find a place called home. The hope is that deciduous trees will eventually take over and crowd out buckthorns, however, it’s necessary to get a crew of hardy folks who will cut down the buckthorns.
-Wild Parsnip - What is Wild Parsnip and why is a dangerous plant?
Wild Parsnip, Pastinaca sativa, is the hobo brother of the garden parsnip. It is a large, tall herbaceous plant. Other members of the parsley family (Umbelliferae) are carrots, celery, and parsley. The difference with the wild parsnip is that its sap causes severe skin problems. When the juice of the leaves, stems and flowers is absorbed by the skin and comes in contact with sun, it causes medium to severe sores that are similar to burns. This is called a phytotoxic reaction. In mild cases, the skin may turn red and feel like sunburn. In more serious cases, the skin reddens, then forms blisters.
Some folks are even allergic to the leaves of the sweet parsnip.
Wild Parsnip, native to Eurasia, is rapidly becoming widespread in abandoned fields, pastures and roadsides throughout northern New England. You can look it up on the web at google.com. It grows along roadways, in ditches and abandoned fields. Unlike benign weeds, it can take over an area with ease, out competing native plants.
If you get a passing burn from exposure to one of these plants, cover it with a cool, wet cloth and call the doctor. It should be treated like a burn, which means it needs to be kept clean with the application of an antibiotic cream.
A Mystery Plant - Can I grow a mystery plant that I can fool my friends with? Being that I just mentioned wild parsnip, I want to describe a most interesting plant, the common sweet parsnip. Parsnips, like beets and Brussels sprouts, are not grown as much as they once were. And yet they are one of the tastiest roots vegetables in my garden universe. The key is to leave them in the ground over the winter and dig them up in the spring when the garden soil begins to thaw. Make sure to throw a little mulch over them in late fall and mark their whereabouts. As far as a mystery plant is concerned, leave two or three parsnips in the ground in the spring and let them grow up over the summer. Give them lots of room to grow. They will form huge, humongous plants which will produce parsnip seed. Very few of my gardening friends have ever been able to identify them. Try them out and "Stump the Chumps."
-Giant Hogweed - The sap from this tall noxious weed, in combination with moisture and sunlight, can cause severe skin and eye irritation, painful blistering, permanent scarring and blindness. Contact between the sap and the skin occurs either through brushing against the bristles on the stem or breaking the stem or leaves. Hogweed can grow up to 14 feet high.
Hogweed is a biennial or perennial herb in the carrot family. The stems grow two to four inches in diameter and have dark reddish, purple blotches. Its large compound leaves can grow up to five feet wide. Go online to identify the plant under "giant hogweed identification." Other plants that look similar are also shown.
Moonflower and Other Toxic Plants - The CDC (Centers for Disease Control and Prevention) have recently stated that teens are trying to get high on the moonflower. Some are ending up in the hospital from eating the seeds or drinking the tea from the seeds. They experience dilated pupils, a rapid heart rate, hallucinations and an inability to urinate. The moonflower is a mature plant, Datura inoxia. It blooms at dusk. Thousands of reports have come into the CDC about toxic plants.
* Another plant that has become a real pest are multi-flora roses.
They can take over a field with ease. They are easy to identify in a pasture.
-Leaves of Three, Let Them Be - Poison Ivy is spreading these days in part because it's getting warmer with climate change. Be careful when trying to remove it. Don't use a weed whacker as you will just spread the oil into the air. You can dig out the roots when their young but make sure and wear gloves, pants and long-sleeved clothing. And wash your clothes and don't put the vines in the compost pile, but send them to the landfill.
This shade-loving vine can cause severe rashes, itching and sores that will spread the poison if you scratch it. When I was a kid, my mom would put calamine lotion on the sores to dry it up. Today, I still use the lotion.
In Montpelier, Vermont, Vermont's capital city, Mary Beth Herbert is trying a natural way to get rid of poison ivy by grazing goats.
Three goats are munching on the plants along the small city's bike path behind the high school and near a river. This causes stress to the poison ivy. It's expected to take several years of cyclical grazing to eradicate the poison ivy. The poison ivy doesn't harm the goats. The city had tried to eradicate the poison ivy but has been unable to do it using organic treatments. The poison ivy has been so bad in 2018 that the city posted signs warning bikers and walkers.
*See below for information on Roundup, a dangerous and powerful
chemical used to kill poison ivy.
* The estimated damage from invasive species worldwide totals more than $1.4 trillion. Once used widely in gardening, landscaping and erosion control, nonnative plants can be found in yards, along roadways, in wetlands. Besides invasive plants, there are insects like the Asian Longhorned beetle which has infested and killed thousands of trees. It could kill 30 percent of urban trees, destroy the maple syrup industry and damage fall foliage. In 2011, the estimated cost from invasive species in the U.S. was $120 billion.
*Check with your State Department of Environmental Conservation, Fish and Wildlife Department or The Nature Conservancy for more information on these invasive plants. It's important to point out that some species are considered invasives in certain states and not in others. Go online for pictures of all these plants.
Tips on Fighting Invasives:
While you're removing and, in some cases, using invasive plants like mustard garlic and Japanese knotweed for your dinner plate, why not spend time collecting many non-invasives plants for the dinner plate? Here are just a few you can gather: fiddlehead ferns, pheasant cut mushrooms from downed trees, wild purple violets, dandelions, stinging nettles, wild ginger, and ramps. This is one way to learn about sustainable foraging.
* Go to The Woodchuck's Guide to Gardening for more on gathering wild plants.
Maine is gathering data through the website iMapInvasive. The online tool allows residents to send photos of invasive plants they encounter on public and private land. Some 224 users have submitted more than 2,800 observations of about 40 non-native plant species. Eight other states including Vermont and our neighbors to the North use the mapping tool.
According to state biologist Nancy Olmstead "The problem with these plants is that they overrun native habitats and crowd native species." For example, giant hogweed has toxic properties that can cause pain and permanent injuries. Other invasives provide good habitat for mice that harbor ticks that carry Lyme disease and other tick-borne diseases. The main invasives include buckthorn, Japanese barberry, Morrow's honeysuckle and dozens of others. Autumn olive is found along a 40-mile stretch of Interstate 295 from Yarmouth to Gardiner. In Acadia National Park 30 plants are considered threatening to the park’s ecosystem.
Many of the plants arrived as ornamental plants through horticultural trade. Others came by accident, such as purple loosestrife, which arrived in the ballast of a ship.
As a counterpoint to all the invasives, just about all the plants we see in spring and early summer are non-invasives. For example, when walking through wetlands, you'll notice skunk cabbage and marsh marigold along with swamp grasses, bittersweet, Joe Pye weed, alders, willow, box elders, and perhaps some elms and butternuts. These are just a few.