Georgia Wildlife Federation

Resources < Wildlife Habitats < Guide to Native Plants of Georgia for Wildlife < Think Again

This may sound silly, but working on this article has given me bad dreams. It all started when I was at a respected, local nursery and noticed for sale a beautiful plant, but one I knew was considered an invasive exotic, beautiful though it was. This made me wonder what other commonly sold plants are invasive and what I may even have in my own yard that I did not realize was a potential problem. The more I have learned about invasive plants, the more concerns I have about my own gardening habits, and I have even awakened some mornings fretting about potentially wayward plants that may outgrow the bounds of my garden to wreak havoc elsewhere in the environment. I have realized I need to think again before assuming that some of those lovely plants offered for sale are quite so lovely after all.

Exotic, alien, introduced, non-native, non-indigenous - all are terms to describe plants that occur in locations beyond their known historical ranges. In other words, they were moved to their current locations by people, rather than by natural means. These plants have reached their destinations in various ways, but most invasive plants were introduced intentionally, either as ornamentals, crop plants, wildlife habitat plants, for medicinal purposes or to assist with erosion control. Many that are now invasive in certain areas of the country, such as dame’s rocket (Hesperis matronalis), ox-eye daisy (Chrysanthemum leucanthemum), and bachelor’s button (Centaurea cyanus), are now so widely naturalized that many people assume that they are native. And sadly, these are often the same plants we see in "wildflower" plantings along our highways. But not all exotic species are harmful, and many are beneficial. As a matter of fact, the large majority of our agricultural plants are non-native.

The problem occurs when a species is extremely aggressive in its growth habit and does significant damage by overtaking desirable species or by affecting the ecosystem. These invasive alien plants typically have several of the following characteristics: a rapid rate of growth and maturity, prolific seed production, successful seed dispersal mechanisms, high germination rates, rampant vegetative spread, and high cost of removal or control. Many are free from natural controls, such as predators and pathogens, allowing them to thrive unchecked. This rapid growth limits the availability of light, water, nutrients and space, and as they overtake existing vegetation, they form dense one-species stands of growth. They can alter the hydrology, soil composition and natural fire patterns of an area. Some even hybridize with native species, resulting in unnatural changes to the gene pool. Others may harbor pathogens that affect the native species. Some are toxic to grazing animals. Some are even allelopathic, meaning that they prevent the growth of nearby plants by secreting poisonous chemicals.

Invasiveness is related to habitat and climate; a plant may be fine in one location and extremely invasive in another. And not all invasive plants are aliens; some are native species which became aggressive spreaders when introduced into a new habitat. For example, the black locust (Robinia pseudoacacia), native to eastern North America, got out of control when it was taken west.

The problem of invasive exotics is second only to habitat destruction as a threat to biodiversity. The scope of the problem is evident when one notes that 42% of the species on the Endangered Species list are there due to competition with invasive species.

So what can we, as individual gardeners, do about this troubling problem? First and foremost, educate yourself. Learn what plants are already known to be a problem in the East and Southeast, especially those that are common landscape plants that you are likely to see sold in nurseries and promoted in the trade. In addition, even be wary of plants that are invasive in other areas of the country. History shows that it may take decades for a plant to spread out of control and become an evident problem. By that point, control may be next to impossible. For this reason, it is best to err on the side of caution. If you have any doubts about a plant, don’t plant it.

Anytime you are evaluating an introduced plant for your landscape, consider the following: if it naturalizes or self sows; how far it spreads; how fast it grows; how its seeds are dispersed and if they will be carried by wind or eaten and spread by animals; if it is allelopathic; if it will be so hardy or drought tolerant that it will out-compete other vegetation.

Don’t assume that if a plant is sold in a reputable nursery or recommended by an "expert" that it is not invasive. As I researched this article, I looked in national gardening catalogs, local nurseries and well-known reference books to see how many of these problematic plants were touted. I was saddened to see invasive plants virtually everywhere I looked. And even worse, there was no mention of their invasiveness. I even saw them listed in "environmentally conscious" literature on xeriscaping. I know they are recommended because of their drought-tolerance, hardiness, rapid growth, etc., but that is just what makes them so invasive.

Once you have educated yourself about the invasive plant problem, you will be a more responsible gardener on your own property, and you may have opportunities to make a difference beyond that. If you are involved with schoolyard projects or community gardens, you can use that work to help educate the public. As native plant lovers, we can all influence the nurseries by informing them about the damage caused by specific exotic plants, discouraging them from selling those plants and by requesting that they stock native or non-invasive alternatives. Remember that "money talks" and if we, as consumers, don’t buy a plant, the nurseries won’t carry it.

A few invasive plants are well known to most of us as weedy plants, and we would not consider intentionally planting them. These include chinaberry tree (Melia azedarach), common Japanese honeysuckle (Lonicera japonica), Japanese knotweed (Fallopia japonica or Polygonum cuspidatum), kudzu (Pueraria lobata), mimosa or silk tree (Albizia julibrissin), multiflora rose (Rosa multiflora) and the running bamboos (such as those in the genus Arundinaria, Phyllostachys, or Pleioblastus). I was extremely surprised to find most of these plants in mail-order catalogs along with beautiful descriptions that could entice an unwitting homeowner to order them.

Below are some of the plants that you are even more likely to find for sale in nurseries or through mail-order catalogs and that are often listed as "recommended" in gardening publications. All of these are invasive in the Southeast and/or East, and you may very well be growing some of them in your garden. If so, remove them from your landscape or at least control them and prevent their spread outside your property. This can be done by pruning to prevent seed dispersal or by mowing or spraying to prevent vegetative spread.

Chinese tallow tree (Sapium sebiferum) – may be recommended for bright fall foliage and attractive white seed clusters; birds eat the seeds and thereby spread the tree; invades wetlands, swamps and moist forest habitats.

Norway maple (Acer platanoides) – a commonly planted street tree; many cultivars available; suppresses growth of vegetation beneath its canopy; seeds are wind-borne and can germinate in deep shade, overtaking woodlands.

Princess tree or empress tree (Paulownia tomentosa) – quickly colonizes disturbed sites and out-competes native trees; grows rapidly and sprouts readily from roots and stumps; winged seeds allow it to spread easily and to great distances; a single tree is capable of producing millions of seeds

Sawtooth oak (Quercus acutissima) – often recommended for wildlife, but has spread into forests, displacing indigenous trees.

Siberian elm (Ulmus pumila) – sold for hedges or as a fast-growing tree; displaces native elms, already under pressure from Dutch elm disease; forms dense thickets, eliminating other species.

Tree of heaven (Ailanthus altissima) – very tough and can grow in poor conditions; grows rapidly, developing into extensive thickets; secretes toxin that kills nearby plants; prolific producer of wind-borne seeds; aggressive sprouter.

White mulberry (Morus alba) – this non-native mulberry hybridizes with the native red mulberry (Morus rubra) and could thereby eliminate the native tree; carries a root disease that kills the native mulberry.

White poplar (Populus alba) – out-competes native trees and shrubs in sunny fields and forest edges; adaptable to a wide variety of soils; prolific seed producer and sprouter.

Autumn olive (Elaeagnus umbellata) – has been recommended for wildlife and erosion control and has been used in roadside plantings; grows rapidly into a dense thicket and can dominate almost any landscape; prolific producer of seeds which are eaten and spread by birds.

Burning bush or winged euonymus (Euonymus alatus) – commonly used as a foundation planting or hedge and for highway plantings; many cultivars are available; grows in wide range of conditions and replaces native shrubs in woodland and other habitats; spread by birds which eat the fruits.

Bush honeysuckles (Lonicera cultivars and species such as L. fragrantissima, L. maackii, L. morrowii, L. tatarica, and others) – rapidly colonize variety of habitats from fields to woodlands, creating dense shade and out-competing more desirable species; some are allelopathic; spread by birds which eat the berries.

Butterfly bush (Buddleia davidii) - often highly recommended as a butterfly habitat plant and widely planted in many landscapes; many cultivars available; has escaped from cultivation and is colonizing disturbed areas such as roadsides.

Japanese barberry (Berberis thunbergii) – common landscaping shrub with many cultivars available; grows well in many conditions and soils; is becoming extremely invasive by overtaking fields and open forest habitats; seeds spread by birds.

Japanese spirea (Spirea japonica) – common in the horticultural trade with many varieties available; has escaped cultivation and spread rapidly, forming dense stands which out-compete many native plants; seeds remain viable for years.

Nandina or heavenly bamboo (Nandina domestica) – common landscaping shrub; berries eaten by birds have resulted in its escape from cultivation; has invaded pine flatwood communities in the Southeast, out-competing native understory vegetation.

Privet (Ligustrum spp. such as L. vulgare, L. sinense, L. japonicum) – widely used as hedges and garden plants; all are extremely aggressive and form dense thickets; prolific producers of seeds which are eaten by birds, thereby spreading the plant; also spread vegetatively.

Scotch broom (Cytisus scoparius) – has become a big problem on the West Coast and is now invading areas in the East and Southeast; spreads by the prodigious production of long-lived seeds and can re-sprout from the roots; displaces native plants and makes re-forestation difficult; flammable, carrying flame to tree canopy, where it is especially destructive.

English ivy (Hedera helix) – one of the most common landscaping ground covers; grows up trees and can eventually pull them down; shade tolerant, making it especially problematic on wooded sites where it overtakes understory species.

Fiveleaf akebia (Akebia quinata) – used as an ornamental on trellises and garden walls; shade and drought tolerant, making it capable of invading many habitats; its rapid growth can kill off ground level and understory vegetation and can even smother canopy trees.

Japanese honeysuckle cultivars (such as Lonicera japonica ‘Halliana’ or ‘Purpurea’) – despite the bad reputation of Japanese honeysuckle, cultivars are still offered for sale, but these are just as invasive as the common honeysuckle; rapid spread smothers ground vegetation, shrubs and trees; spread by birds.

Oriental bittersweet (Celastrus orbiculatus) – popular because of colorful berries in fall, but aggressively strangles and shades out native plants; is displacing the native American bittersweet (C. scandens), even hybridizing with it; seeds dispersed by birds; also reproduces vegetatively.

Periwinkle or vinca (Vinca major, V. minor) - has long been used as a garden plant, and has escaped cultivation; long-lived and persistent; spreads vegetatively to crowd out understory plants in wooded sites.

Porcelain berry (Ampelopsis brevipedunculata) – receiving strong recommendations from garden centers due to its attractive berries; covers and crowds out native plants at woodland edges, fields, open habitats; seeds have high germination rate; also spreads vegetatively.

Wintercreeper or climbing euonymus (Euonymus fortunei) – forms dense mats of vegetation in shade or sun, out-competing other species; also climbs by aerial roots, damaging trees; tolerates a variety of conditions; seeds dispersed by birds.

Chinese wisteria (Wisteria sinensis), Japanese wisteria (Wisteria floribunda) – strangles and shades native trees and shrubs and can kill even large trees; tolerates a variety of soils and conditions; very long-lived; spreads from seeds and stolons.

Chinese silver grass or eulalia (Miscanthus sinensis) – popular ornamental grass; spreading to disturbed sites, roadsides, forest edges and clearings; persistent once established.

Fountain grass (Pennisetum setaceum) – a popular ornamental, but can be an aggressive colonizer of many habitats, out-competing native species; wind-dispersed seeds remain viable for years.

Giant reed (Arundo donax) – introduced as an ornamental, for erosion control and as a wind break; invades freshwater habitats in warmer areas of the country; spreads by rhizomes and can cover huge areas; highly flammable, re-sprouting after burning; a large threat to riparian habitats and can easily spread downstream.

Pampas grass (Cortaderia selloana and C. jubata) – has been a problem on the West Coast, but is now becoming invasive in the East; seeds are dispersed long distances by wind and germinate readily in open, sandy soils, making it a threat in coastal areas.

Reed canary grass (Phalaris arundinacea) – sold as an ornamental and for erosion control, this grass is now invading wetlands; spreads vegetatively, covering large areas at the expense of native wetland species.

Beefsteak plant or Japanese perilla (Perilla frutescens) - sold as salad plant, and ornamentally for its dark purple foliage; seeds invasively.

Cardoon or wild artichoke (Cynara cardunculus) – sold as an ornamental; spreads into a variety of habitats, including those with clay soils; displaces native annuals, perennials and grasses.

Dame’s rocket (Hesperis matronalis) – introduced as a garden plant in colonial days and still sold as an ornamental; often included in wildflower mixes for meadow or roadside plantings; can dominate moist areas of meadow, forest edge and woodland, crowding out native plants; spreads rapidly from seed.

Purple loosestrife (Lythrum salicaria, L. virgatum) – has been declared a noxious weed in many states, and a half-million acres are infested annually in U.S.; especially invasive in damp or wet habitats; cultivars are marketed as sterile and sold at nurseries around the country, though cultivars can breed with wild plants and produce highly fertile seeds; prolific seed producer, each plant producing over 2 million seeds; also reproduces rapidly through underground stems.

Water hyacinth (Eichhornia crassipes) – commonly sold as a floating plant for ornamental ponds; has become one of the worst weeds in warmer waters of the U.S.; forms a solid mat on the water’s surface which shades out underwater plants, crowds out surface vegetation, changes water temperatures and disrupts the food chain.

Yellow flag iris (Iris pseudacorus) – this is a popular iris for planting in ornamental ponds, however if used in a non-contained situation such as on stream banks or natural ponds, it can spread rapidly, colonizing wetlands and displacing native species.