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Resources < Wildlife Habitats < Guide to Native Plants of Georgia for Wildlife < Beware of the Weeds
By Leslie Kimel
Growing up, my sisters and I were very lucky because behind our house we had woods to play in. They were beautiful, shady woods, North Florida woods—not very big, but terribly interesting, with a creek and great old live oaks like haunted castles. There was a swampy part with silvery sweetbay trees, and everywhere there were Tarzan vines to swing on. We made trails and tree forts; in fact, we slept so often in the trees that our blankets began to smell like big leaves. Back then we made up names for all the plants we saw under the canopy, because we didn’t know their real ones. I know them now. In our woods we had dwarf palmetto, devil’s walkingstick, American beautyberry, Virginia creeper, trumpet vine, Christmas fern, southern lady fern, sensitive fern, ebony spleenwort, partridgeberry, muscadine grape, wild violet, wild petunia, elephant’s foot, and haircap moss. And that’s just for starters. There was so much more that was delicate, green, and intriguing.
Today, thirty years later, the woods are still there, behind my parents’ house, but they are completely different—the same size, yet eerily diminished. In the shrub and herb layers, just three plants predominate now, all invasive exotics, escapees from my parents’ yard and the yards of their neighbors. They are English ivy, nandina, and ardisia—very popular landscaping plants in Florida—and all three are found on the Florida Exotic Pest Plant Council’s “List of Florida’s Most Invasive Species.” Three plants—that’s just about all you’ll see now, in a place that was, a relatively short time ago, diverse and complex. All the subtlety is gone from our woods. All the wonderful sense of surprise, the possibility of discovery. Our woods are boring, ruined.
I live in Georgia now, but I haven’t escaped the problem of invasive exotic plants. They line the highways I travel on my way to work and fill the vacant lots in my neighborhood. They sprout up in my yard and invade the parks and natural areas I visit. Invasive exotic plants make every place they spread less healthy and less interesting. In fact, experts have begun to refer to invasive species as “biological pollution.”
But what is an invasive exotic plant exactly? Let’s start by defining the word “exotic”: An exotic plant is simply a plant that has been introduced (by people) into an environment in which it did not evolve. An invasive exotic plant is a non-indigenous plant whose growth and spread is so rapid and aggressive that it threatens to overwhelm native plant communities and natural ecosystems.
Not all exotic plants are invasive, and many are beneficial (corn, wheat, and oats are not native to North America). So why do some exotics become invasive while others don’t? According to the Brooklyn Botanic Garden’s Invasive Plants: Weeds of the Global Garden, invasive exotic species typically exhibit some or all of the following characteristics: rapid maturation, reproduction by both seed and vegetative growth, long flowering and fruiting periods, prolific seed production, and seed dispersal by animals. On their home turf, these vigorous plants are kept in check by a variety of natural controls, including predators and pathogens. When carried outside their natural range, they run rampant because these controls are not present.
Invasive plants aren’t always from far-off foreign countries; they might simply come from another region of our own country, or even another region of our own state. For example, some experts are now concerned that cherrylaurel (Prunus caroliniana), a native of Georgia’s Coastal Plain, is showing invasive tendencies in the Piedmont.
Invasive exotic plants have already infested over 100 million acres in North America and are invading an additional 4,600 acres each day. The impact of invasive exotics on the environment is devastating. Plant invaders destroy biodiversity, the complicated network of life that is the key to healthy, functioning ecosystems. They displace native plants and the wildlife that rely on these plants for food and shelter. They alter fundamental ecosystem processes, including fire regimes and hydrological patterns. They disrupt native plant-animal associations (including pollination and seed dispersal) and harbor non-native animals and pathogens (kudzu serves as an egg-laying site for gypsy moths). As Sara Stein explains in Planting Noah’s Garden, her popular book on restoring backyard ecosystems, “[Invasive exotics] degrade habitat. They kill ecosystems. They alter water and soil chemistry. They drastically reduce diversity. They abort succession. They cause animals to abandon the site. They leave their habitats biologically moribund.”
According to the National Wildlife Federation, invasive exotic plants cost our national economy at least $36.6 billion annually. Invasive exotics clog waterways and fuel wildfires. They reduce crop yields and interfere with harvest operations. They out-compete palatable forage for livestock on rangelands and reduce the productivity of our forests and fisheries. They also create costly aesthetic problems: Removal of non-indigenous weeds from American golf courses costs $1 billion each year. Of course, the economic costs are nothing compared to the ecological ones. Experts now suspect that invasive exotic plants are responsible for destroying more natural habitat each year than is destroyed through land development.
Out of the thousands of exotic plant species that persist outside of cultivation in North America, about 350 are considered dangerously invasive. Some invasive plants arrived here accidentally, but many were purposefully introduced and planted with the best of intentions. They were planted to control erosion and provide forage for cattle. They were even planted to improve wildlife habitat. Many were introduced as ornamentals. In fact, about half of our most aggressive and damaging plant invaders were brought here simply to decorate our yards and gardens, and dozens remain popular sellers at nurseries today.
Below, you’ll find photos and descriptions of some of Georgia’s worst weed offenders. If you want to help protect the diversity of our precious parks and natural areas, don’t plant any of these plants! You say these thugs are already present in your landscape? Get rid of them! Digging and pulling will work for smaller plants, but larger ones will probably have to be cut down and the stumps painted with herbicide—repeatedly. Persistence is the key. Profiles of more exotic invasives are on the way, but for now, here are ten plants to watch out for:
Chinese Privet (Ligustrum sinense): When it was introduced to the United States from China in 1852, this twelve-foot shrub was touted as a pest-free, disease-free alternative to common privet (Ligustrum vulgare). Its fluffy white flowers, evergreen foliage, and general toughness made it an instant hit, and by the turn of the century, nearly every Southern garden had a Chinese privet hedge. By this time, too, Chinese privet was already invading natural areas across the region, especially low woods, bottomlands, and streamsides.
Today, Chinese privet is ubiquitous in Georgia. It is such a successful thug because it is fast growing and extremely adaptable, thriving in a wide variety of soil types and in both shade and sun. More importantly, it reproduces like crazy, sending up root suckers and producing copious fruits. Privet fruits are part of the winter diet of robins, cardinals, cedar waxwings, European starlings, bluebirds, and sparrows, but the dark, berry-like drupes are low in lipids (fat) and aren’t terribly nutritious.
Chinese Wisteria (Wisteria sinensis): Chinese wisteria is a deciduous, high-climbing, twining woody vine with velvety, bean-like seedpods and pinnately compound leaves up to 16 inches long. Clusters of fragrant purple flowers appear in spring, resembling long, lush bunches of grapes. Since its introduction in the early 1800s, Chinese wisteria has been a staple in Southern gardens. In the old days it was commonly used for decorating front porches; today, it is usually trained on an arbor or trellis.
But as pretty and popular as this vine is, it is not a good choice for our landscapes. It grows at an unbelievably rapid rate, overrunning shrubs and herbaceous plants, shading them out, and twining around trees, eventually strangling them. An established vine might be 15 inches thick and 70 feet long! Provided with a little sun, Chinese wisteria will thrive in just about any soil type and in both wet and dry conditions. In riparian areas, seeds are often dispersed by water.
Multiflora Rose (Rosa multiflora): A native of Japan, Korea, and China, multiflora rose is a robust ten-foot shrub with arching, thorny stems; its compound leaves are each composed of five to ten one-inch, oval-shaped leaflets. In May and June, showy clusters of single white flowers appear, followed by a profusion of bright red hips, which persist into winter. Hungry birds eat the hips, spreading the seeds to pastures, fields, roadsides, and forest openings.
Because of its popularity with the birds, multiflora rose was once commonly planted by wildlife managers. In the 1930s it was promoted as a living fence for soil conservation. Unfortunately, the plant is extremely aggressive and any good it might do can’t possibly make up for the habitat it destroys.
Japanese Honeysuckle (Lonicera japonica): Japanese honeysuckle is a trailing or twining woody vine featuring fragrant, two-lipped, yellow and white flowers in spring and blue-black berries in fall. The oval-shaped leaves are semi-evergreen to evergreen and occur in pairs along the stem. Native to eastern Asia, Japanese honeysuckle has been planted in the South as an ornamental since the 1860s. It has also been used to control erosion and provide food for wildlife.
Japanese honeysuckle invades a wide variety of habitats, including forests, fields, and wetlands. Disturbed areas are especially vulnerable. Dense growth of Japanese honeysuckle depletes soil moisture and limits the amount of light available to more desirable plants. As it climbs, Japanese honeysuckle can get so heavy that it causes its host tree to topple. It kills shrubs and young trees by twisting tightly around their stems and cutting off the flow of water and nutrients.
English Ivy (Hedera helix): Despite its aggressiveness, this evergreen woody vine (and European import) has remained tremendously popular with American gardeners for over 200 years. Now present in 28 states, it is still very commonly sold and planted as a groundcover. English ivy features dense, dark green, waxy leaves; small greenish-white fall flowers; and fleshy black fruits in spring. English house sparrows, European starlings, robins, and other songbirds eat the fruits and disperse the seeds. The vine also reproduces vegetatively. Highly adaptable, it thrives in full sun and dense shade, in moist areas and dry ones, and in a variety of soil types.
When English ivy spreads beyond its intended borders, as it inevitably does, it causes tremendous damage. Racing along the ground, it forms a thick evergreen mat that shades out other plants. It dashes up trees, wrapping around branches and twigs and preventing sunlight from reaching its hosts’ leaves. Infested trees are more likely to blow over during storms; this is due to their weakened state and the sheer weight of the vines they are carrying.
Mimosa (Albizia julibrissin): Native throughout Asia, from Iran to Japan, mimosa was introduced to North America as an ornamental in 1745. A medium-sized, short-lived, fast-growing tree, it is well known for its nectar-rich summer flowers that look like pink powder puffs and smell like ripe watermelon. Other distinguishing features include feathery leaves, pale bark, and long, bean-like seedpods. This is a pretty tree (it even attracts hummingbirds), but plant one and you’ll soon have dozens.
Mimosa produces huge crops of seed and will re-sprout with amazing swiftness after being cut. Seeds are protected by an impermeable coat and remain viable for years. Mimosa isn’t at all fussy when it comes to soil, but it does prefer a sunny spot. Flourishing in disturbed areas, it can be found in vacant lots, along roadsides, and at the edges of parking lots.
CHINESE TALLOW TREE
Chinese Tallow Tree (Sapium seberiferum): In China this medium-sized tree has been cultivated for 1,500 years as a seed-oil crop. In the Southeast it has been planted as an ornamental since the 1700s. It is still sold in Southern nurseries despite the fact that it is displacing native plants and radically altering marshes and forests throughout the region. People like Chinese tallow because it grows fast, resists pests, and turns bright red in fall. It features tassel-like clusters of yellow-green flowers in spring, and in late summer it decorates itself with intriguing bunches of large white seeds that resemble popped popcorn.
Don’t let its good looks fool you. This tree is one of the greatest threats to habitat in south Georgia. Chinese tallow tree starts producing seed when it is just three years old, and a mature tree can produce as many as 100,000 seeds. These are dispersed by birds and also by water (seeds can float). Chinese tallow suckers like mad, too. It thrives in just about all habitat types—everywhere from upland forests and vacant lots to wet prairies and the shores of lakes and rivers.
Tree-of-heaven (Ailanthus altissima): With its large compound leaves, a young tree-of-heaven might easily be confused with sumac—but not for long. This fast-growing plant soon gets much bigger than a sumac ever would; it can reach heights of 80 feet or more. Its rough, light gray bark looks a lot like the skin of a cantaloupe, and its spring flowers are yellow-green. The crushed leaves smell like rancid peanut butter.
In 1784 tree-of-heaven was brought to North America from China for ornamental purposes. It was later planted because of its medicinal properties (in traditional Asian medicine it is used to treat asthma and other disorders). Now the tree is found in 42 states, including Georgia, in vacant lots, forest openings, farm fields, and fencerows, and along roadsides and railroad tracks. There are lots of reasons for tree-of-heaven’s success. Female trees produce huge amounts of seed, and that seed germinates at very high rates. The plant also spreads vegetatively. Saplings grow so fast (up to four feet per year!) that they can outpace any native tree. Tree-of-heaven is also allelopathic, meaning it secretes toxins that restrict the growth of other plants. It thrives in drought, cold, poor soil, and air pollution.
Kudzu (Pueraria montana): A perennial trailing or climbing vine, kudzu is easily recognized by its hairy stems and big fuzzy trifoliate leaves. In summer it sports velvety purple flowers that smell almost exactly like Nehi Grape soda. Under ideal conditions kudzu can grow as much as a foot a day and 60 feet per year. When land is overrun by kudzu, it becomes a biological desert.
Introduced to the United States in 1876 at the Centennial Exposition in Philadelphia, kudzu captivated American gardeners right away, and kudzu-draped porches immediately became the rage. When it was discovered that animals would eat kudzu, people only planted more. Throughout the Depression the Soil Conservation Service advocated the planting of kudzu for erosion control, and in the 1940s farmers were paid up to $8 an acre to plant fields of the vine. Today, kudzu covers over seven million acres in the South.
Nepalese Browntop (Microstegium vimineum): Nepalese Browntop is an annual grass from Asia. It was introduced to North America in the early 1900s in a most unusual way: Dried Nepalese browntop was used a packing material to protect delicate porcelain during shipping. The plant is now present in 23 states.
Nepalese browntop thrives in moist, shady areas, especially stream banks and floodplains, and will rapidly colonize disturbed spots. Lacking any predators (deer won’t even browse it), it displaces native plants and quickly covers large areas as a monoculture. Nepalese browntop is easy to recognize because it looks like a tiny bamboo and has a silvery stripe down the midrib of each leaf. One small plant can produce 1,000 seeds. The seeds are dispersed by water and by clinging to the fur of passing animals.
This is only a small sampling of the invasive exotic plants that threaten Georgia’s biodiversity. There are scores more, including periwinkle (Vinca major and Vinca minor), yellow flag iris (Iris pseudacorus), princess tree (Pawlonia tomentosa), autumn olive (Elaeagnus umbellata), golden bamboo (Phyllostachys aurea), hydrilla (Hydrilla verticillata), chinaberry (Melia azedarach), common broomrape (Oranbanche minor), Japanese climbing fern (Lygodium japonicum), bush honeysuckle (Lonicera maackii, L. morrowii, and L. tartarica), nandina (Nandina domestica), and Chinese silver grass (Miscanthus sinensis). If you’d like to learn more about invasive exotic plants, the Georgia Exotic Pest Plant Council has reorganized and is meeting again. Their web address is www.gaeppc.org. For a list of Georgia nurseries that sell native plants, visit the Georgia Native Plant Society’s website at www.gnps.org.
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