ALIEN INVASION: ATTACK OF THE NONNATIVES

BY WES DUREN, LANDSCAPE & CONSTRUCTION SUPERVISOR

Numerous plants throughout Ohio that were once sold for ornamental gardens, livestock forage, food, medicine, and erosion control have escaped cultivation, and now threaten our delicate ecosystems and natural habitats. Approximately 50,000 non-native species have been introduced to the United States and at least half this number (25,000) is plants. Most invasive plants are foreign intruders and grow much faster than plants indigenous to our area. Native plants are considered those that were growing in our area before European settlement. Our native plants are under attack; their very existence is endangered by plants that thrive and spread aggressively outside their natural range. By crowding out native plants that our wildlife depends on for food and habitat, invasive plants are detrimental to both native plant and wildlife communities. Together, we can wage war against the hordes of alien plant invaders by eradicating and replacing them with native vegetation that sustain our wildlife and provide us year-round interest.

An invasive plant species that lays claim to a new area may gain an unfair advantage over native plants since the insects, disease and foraging animals that naturally keep its growth in check are not present in its new ecosystem. Of these oversea aggressors, the most notorious hail from Asia, and are known as honeysuckle. There are three species of the ubiquitous shrub honeysuckle: Lonicera maackii, L. morrowii and L. tartarica, and one species of vine honeysuckle, L. japonica. Honeysuckle was planted throughout Ohio from the 1950s through 1970s. Several state forestry and wildlife agencies promoted bush honeysuckle as a great ornamental in the urban landscape. It was also touted as a great way to control erosion, and to create wildlife cover and food sources. Honeysuckle was classified as invasive in the 1980s and has been smothering native trees, shrubs and perennials at an alarming rate. Once honeysuckle gains a foothold in a woodland area, it quickly shades the forest floor, preventing young trees and shrubs from growing to maturity. Though it was touted as a great food and cover source to wildlife, it did the opposite. Wildlife is left more exposed to predators, and the berries contain no nutritional value to the birds that eat them. There are three ways to naturally remove honeysuckle without the use of toxic herbicides. The first method is to dig around the shallow root system and pop the plants out of the ground by hand or with the help of a Bobcat. The second technique is to cut the honeysuckle level with the ground and then kick or whack all green succulent off shoots for two to three seasons, or until the shoots cease. By not allowing the new shoots to mature, you will eventually exhaust the honeysuckle and the root system will rot in the ground. The third method can be achieved by cutting the honeysuckle level with the ground and then covering the stump with a 4’x4’ section of nylon woven weed fabric, staked firmly into the surrounding soil. Keep the weed fabric in position for at least two full growing seasons for best results. Native shrubs and trees will readily replace honeysuckle once removed.  Some native plants worth considering are: spicebush, elderberry, silky and redtwig dogwood, blackhaw and arrowwood viburnums, witch hazel, Carolina allspice, oak, Carolina silverbells, flowering dogwood, serviceberry, or try cross vine and native trumpet honeysuckle vine as twining plant options.

One of the most beautiful invasive plants in the U.S. is purple loosestrife, lythrum salicaria. The 15-inch showy, magenta flower spikes rest atop three-foot tall stems, appearing from July to early October. Purple loosestrife is an invasive perennial plant that is spreading rapidly in North American wetlands, shorelines and roadside ditches. Thick stands of purple loosestrife crowd out native plants and reduce food, shelter and nesting sites for mammals, birds, turtles and frogs. After multiple introductions in the 1800s for bee keeping, as an ornamental and medicinal plant and in discarded soil used as ballast on ships, this European species has invaded nearly every U.S. state and at least six Canadian provinces. In the last 20 years, at least 24 states have banned the sale and planting of the perennial, including Ohio. That means it is illegal to cultivate, divide or share purple loosestrife with friends and family. Like honeysuckle, purple loosestrife has no natural predators, allowing it to run rampant in wet areas. A single plant can produce as many as 3 million seeds per year! The Nature Conservancy estimates about $45 million a year is spent to control this foreign invader. The root system of loosetrife is thick and woody, making it difficult but not impossible to eradicate. Three host specific beetles approved by the USDA were released in 1992 to help eat and control purple loosestrife. Many are concerned that releasing nonnative insect species may actually create more ecological damage in the long run. Promising results have been seen though, as these beetles continue to devour loosestrife across the United States and Canada. The best control for any invasive weed however, is prevention. By digging this perennial out of our gardens and burning it and avoiding purchasing this plant, we will be helping to promote wildlife conservation. Many native perennial species can be used to provide similar interest such as gay feathers, cardinal flowers, blue lobelia, queen of the prairie, bee balm, blue giant hyssop, swamp milkweed, Joe Pye and purple coneflower.
           
Another invader from afar is garlic mustard, alliaria petiolata, which was shipped from Europe as a medicinal panacea and culinary herb. Plants can be easily recognized by a garlic odor that is present when any part of the plant is crushed and also by the strongly toothed, triangular leaves. An extraordinary shade tolerance allows this plant to invade high-quality, mature woodlands, where it can form dense stands. These stands not only shade out native woodland flora, but also produce chemical compounds that inhibit seed germination of other species more important for wildlife. Flowers are continuously produced at the top of the long stalk from late April through mid May and are white with four petals that form a cross. Garlic Mustard can produce up to 8,000 seeds per plant and can lay dormant in the soil for over a decade, waiting for perfect conditions to germinate.  This seemingly delicate biennial is wreaking havoc on our natural wildflower and tree populations because it produces fungicidal chemicals that reduce beneficial fungi in the forest floor, making it nearly impossible for wildflowers and trees to obtain hard to reach nutrients without its symbiotic soil partner, mycorrhizal fungi. This weed is easy to pull out of the ground but should be burned once collected. If pulled and left to lie, the seeds will often germinate and develop, despite being pulled. One year’s seed produces ten years worth of weeds, so remain diligent when ridding your woodlands of garlic mustard and other invasive weeds. If you can’t beat 'em, eat 'em! Garlic mustard can be used in many culinary dishes including quiches, soups, stews, sautéed with other vegetables or made into a pesto, and imparts a unique garlic essence. The young tender leaves are most palatable. Native woodland plants that will replace garlic mustard are goats beard, wood asters, palm sedge, American coralbells, viola species, most ferns, may apple, trout lilies, jack-in-the-pulpit, trillium, wood aster, wild ginger and foam flowers.
                       
There are many additional trees, shrubs, perennials and grasses that are all-encompassing and highly invasive, which we should try to avoid in our landscapes and eradicate when possible. Some of these aggressive plants are callery pear (Bradford pear), burning bush, Japanese knotweed, Canadian thistle, crown vetch, autumn olive, reed grass, Asian bittersweet, poison hemlock, wintercreeper and periwinkle. There is always a safe and natural approach to eliminate persistent weeds in your yard, so you no longer need to subject yourself or those you love to cancer causing chemical herbicides. 

Marvin’s Organic Gardens would be glad to help recommend our nontoxic weed control products or weed eradication services to ensure that you rid your yard of noxious weeds, naturally! We invite you to our Garden Center, where you can also view many superb native and edible plant options to help fill the weedy voids in your yard. It is often as simple as selecting plants that are bigger, badder, bolder and more beautiful than the invasive weeds. Go organic. It’s only natural!