What Can I Do About Invasive Plants? The best insurance against future problems is to avoid the use of known invasive plants and educate others about the problems of invasive species. This website lists many of the plants that are considered invasive in Pennsylvania. Plants on this list should not be used around your home or community because they can escape cultivation and aggressively move into surrounding ecosystems. Avoid invasives by choosing plants that are native to your area. Natives often are adapted to a specific environmental niche, and have natural controls that keep them in balance. Minimize landscape disturbance. Invasive plants thrive on bare soil and disturbed ground where the native plant community has been displaced. The key to controlling invasives is to protect healthy native plant communities. Use fertilizers wisely. Proper site preparation begins with a soil test before applying fertilizer. High nitrogen levels sometimes give an advantage to invasive species that are better adapted to using plentiful nutrients for explosive growth. For soil fertility, try using organic, slow-decomposing compost and mulches  Have a land management plan for maintenance over time. It makes sense when designing a property to plan for future maintenance. Lawns are maintained by weekly mowing, while gardens are often hand-weeded. Meadows in Pennsylvania may need to be mowed every year. Woodlands are probably the lowest-maintenance landscape, but they too will need to be monitored and invasive plants removed. Scout your property annually for invasives or other problems. The best way to control invasives is prevention, and prevention can only happen through vigilance. Listed on this web site are resources to help property owners. Remove invasives before they are a problem. Effective scouting or monitoring means that problems are found while they are still small and easily controllable. For instance, do not let invasive plants go to seed. Mechanical removal through digging or cutting is preferred. Large populations of invasives may need to be stopped chemically with spot applications of herbicide by trained individuals or by homeowners carefully following label instructions. Replace invasive plants with native or noninvasive species. Invasives are good at exploiting bare soil and empty niches. When you remove an invasive plant, unless there is another plant substituted, the invasive will tend to come right back. What grows in the future depends largely on what is there now; so it is important to fill that niche with a desirable plant that will provide seed for the future. Remove invasives as they appear while their densities are low. This gives the most immediate success because invasive plant control works best where there is a functioning native plant community still in place which can move right into the empty niche.
 Characteristics of Invasive Plants Invasive plants are noted for their ability to grow and spread aggressively. Invasive plants can be trees, shrubs, vines, grasses, or flowers, and they can reproduce rapidly by roots, seeds, shoots, or all three. Invasive plants tend to: not be native to North America; spread rapidly, reproducing by roots or shoots; mature quickly; and if spread by seed, produce numerous seeds that disperse and sprout easily. Invasives are typically generalists that can grow in many different conditions and are exploiters and colonizers of disturbed ground. Impact of Invasive Plants Invasive species should not be used in our landscape because they are degrading our native plant communities and ecosystems. In fact, second only to habitat loss, invasives are a major factor in the decline of native plants. Plants like kudzu, purple loosestrife, and garlic mustard are displacing native plants and degrading habitat for native insects, birds, and animals. Endangered, rare, and threatened native species of plant and animals are especially at risk because they often occur in such small populations that make them particularly vulnerable. A very practical reason to avoid using invasive plants in your landscape is that they escape, spread and require regular weeding to manage even when grown in a cultivated yard. In urban and suburban areas the worst weeds are escaped ornamentals like Japanese honeysuckle, multiflora rose, Japanese knotweed, tree-of-heaven and oriental bittersweet. In yards, gardens, fields, and parks these plants are very expensive to control. Invasive Hitchhikers People can accidentally spread invasive species when they go for a hike, take their boat out on an infested lake or go hunting. Seeds from some invasive plants can stick to clothing or get lodged in the tread of boots and shoes. Some aquatic invasives have tiny larvae that can spread on fishing tackle, waders and boats. Preventing the spread of these invasive species is much easier than trying to control them once they have become established, so it is essential that when people spend time outdoors they are cautious about where they travel. The factsheets listed below give simple tips to lower the chance that you will spread invasive species. ATV Riders Bikers Bird Watchers Boaters Campers Equestrians Fishers Hikers Hunters and Trappers Leased Campsite Owners Trail Maintainers Wildlife Watchers
Amur maple, Acer ginnala, is a small ornamental tree that spreads by numerous winged seeds. Norway maple, Acer platanoides, a common street and lawn tree that frequently escapes cultivation. Sycamore maple, Acer pseudoplatanus, a tall Eurasian tree invading urban and suburban woods in southern PA. Tree-of-heaven, Ailanthus altissima, grows throughout PA. Another immigrant from China introduced as an ornamental. Mimosa, Albizia julibrissin, has escaped cultivation to invade roadsides and woodland edges in eastern PA. Japanese angelica tree, Aralia elata, has sharp spines on the trunk and resembles our native devil's waking stick. Paper mulberry, Broussonetia papyfera, is a common, small ornamental tree from Asia. White mulberry, Morus alba, is a fast-growing species that will hybridize with our native red mulberry, Morus rubra. Princess-tree, Empress-tree, Paulownia tomentosa, imported from China this purple-flowered tree has spread across southern PA by winged seeds. Corktrees, Phellodendron amurense, P. japonicum, P. lavallei, these Asian trees are problematic in urban and natural areas in southeastern PA. Callery pear, Pyrus calleryana, has established populations in fields and hedgerows in southeastern PA. Bee-bee tree, Tetradium daniellii, is an uncommon landscape tree that is slowly spreading in south-central and southeastern PA. Siberian elm, Ulmus pumila, a fast growing tree reaching 50-70 feet high.
Butterfly bush, Buddleja davidii, has numerous cone-shaped bunches of purple flowers that attract butterflies. Russian olive & Autumn olive, Elaeagnus angustifolia and E. umbellata, imported from Asia, have become serious weeds in southern PA pastures and other open ground. Winged euonymus or Burning-bush, Euonymus alatus, a shrub from China and Japan imported for its bright purple-red fall color and frequently found along streams and in woods mostly in southern PA. Privets, Ligustrum species imported from Europe and Asia are aggressive, thicket forming shrubs. Shrub honeysuckles, five Lonicera species that rapidly invade and dominate field edges and pastures. Common buckthorn and Glossy buckthorn, Rhamnus cathartica and R. frangula (syn. Frangula alnus). Small trees or shrubs to 20' high with yellow sapwood and pink to orange heartwood. Jetbead, Rhodotypos scandens, is a deciduous shrub with clusters of small black fruits and white four-petaled flowers. Multiflora rose, Rosa multiflora, this import from Asia has become a noxious weed in PA field, pastures and woodlands. Wineberry, Rubus phoenicolasius, imported from Asia for its raspberry-like fruit and now common on roadsides and in woods and thickets. Japanese spiraea, Spiraea japonica, was imported from Japan for its pink flowers. It escapes from cultivation to forest openings and meadows. Guelder rose, Viburnum opulus, a tall shrub with maple-like leaves imported from Eurasia and escaped to woods fields and roadsides.
Five-leaf akebia, Akebia quinata, a woody twining vine from Asia that has escaped cultivation to disturbed woods in southeastern PA. Porcelain-berry, Ampelopsis brevipedunculata, a deciduous, woody, perennial vine in the grape family imported from Asia. Oriental bittersweet, Celastrus orbiculatus, a twining woody vine imported from Asia and rapidly replacing the native bittersweet in woods and fencerows. Wintercreeper, Euonymus fortunei, is an evergreen woody vine that aggressively invades forest edges and openings. English ivy, Hedera helix, is a common evergreen climbing vine in the landscape that can smother native vegetation. Japanese hops, Humulus japonicus, is a prickly vine that invades moist, sunny areas. Japanese honeysuckle, Lonicera japonica, a common ornamental vine from Asia now an abundant weed in roadside thickets, woods and fields across southern PA. Mile-a-minute weed, Persicaria perfoliata, a slender annual vine with reflexed prickles was accidentally introduced from Asia with nursery stock and now a noxious weed in PA. Kudzu, Pueraria lobata, a vigorous half-woody vine introduced from Asia for ornament, forage and erosion control and now an uncommon but officially noxious weed in southeastern PA. Common and Bigleaf periwinkle, Vinca minor and V. major, are evergreen, ornamental groundcovers that can form thick mats, even under dense tree canopy. Black and Pale swallow-wort, Vincetoxicum nigrum and V. rossicum, are twining vines that can dominate old fields and poison livestock. Chinese and Japanese wisteria, Wisteria sinensis and W. floribunda, are long-lived woody vines with bright purple flowers that can out-compete and smother native vegetation.
Small carpetgrass, Anthraxon hispidus, is native to Asia. It is currently found in a few counties in southern PA, usually alongside invasive stiltgrass. Cheatgrass or Downy brome grass, Bromus tectorum, accidently introduced from Europe in ballast soil or impure wheat seed shipments. A serious agricultural weed in the midwest and western states. Japanese stiltgrass, Microstegium vimineum, introduced from tropical Asia in packing material and spreading through moist areas open woods and clearings across southeastern PA and probably elsewhere. Chinese silvergrass, Miscanthus sinensis, is a tall bunched grass that spreads through vigorous roots and rhizomes. Wavyleaf basketgrass, Oplismenus hirtellus, is a fast-growing, creeping grass not yet in PA but found across the border in Maryland. Reed canary grass, Phalaris australis, forms dense monocultures in wet habitats that disrupt waterways and degrade habitat for native wildlife. Common reed, Phragmites australis, a very large perennial grass, forms extensive colonies in wetlands. The scattered native American populations are being replaced by the vigorus European subspecies. Golden bamboo, Phyllostachys aurea, is a very tall grass with round, hollow stems that spreads rapidly via its underground rhizomes. Rough bluegrass, Poa trivialis, is a non-descript grass that outcompetes native grasses. Ravenna grass, Saccharum ravennae, is also known as hardy pampas grass. It grows up to ten feet tall and quickly colonizes wet habitats. Tall fescue, Schedonorus arundinaceus, is a very common cool season perennial grass that adapts to a variety of conditions and crowds out native vegetation. Shattercane, Sorghum bicolor was imported from Africa as a forage crop but is now a noxious weed in Pennsylvania. Johnsongrass, Sorghum halepense, is native to the Mediterranean region. It is designated as a noxious weed in Pennsylvania.
Goutweed, Aegopodium podagraria, imported from Eurasia and frequently found in fields, thickets, woods and roadsides throughout PA. Garlic-mustard, Alliaria petiolata, a weed of shady moist spots in suburban gardens, woods and floodplains throughout PA; introduced from Europe. Wild chervil, Anthriscus sylvestris, is a member of the carrot family that competes with native plants and carries a virus that can infect some vegetable crops. Narrowleaf bittercress, Cardamine impatiens, is a member of the mustard family native to Europe. Musk thistle, Carduus nutans, is also known as nodding thistle from the way the flowers droop once mature. Black, Brown and Spotted knapweeds, Centaurea nigra, C. jacea, C. stoebe micranthos, have pink to purple flowers that resemble small pineapples. Greater celandine, Chelidonium majus, is a four-petaled yellow flower from Europe that is poisonous. Canada thistle, Cirsium arvense, imported from Eurasia (not Canada) now common and noxious weed in fields pastures and roadsides throughout PA. Bull thistle, Cirsium vulgare, is a large-flowered thistle with long spines and abundant seeds. Poison hemlock, Conium maculatum, was brought to U.S. gardens from Europe in the 1800s it now invades native plant communities in riparian woodlands, open floodplains and stream banks. Crown-vetch, Coronilla varia, a sprawling perennial native to southern Europe planted extensively along highways. It spreads into open, grassland and prairie habitats. Jimsonweed, Datura stramonium, is a state noxious weed that is highly toxic and frequently found in cultivated fields and other disturbed sites. Hairy willow herb, Epilobium hirsutum, is an ornamental perennial with showy, rose-colored flowers that can quickly form dense stands. Goats rue, Galega officinalis, is a state and federal noxious weed that is very poisonous to livestock. Orange day-lily, Hemorocallis fulva, is a very hard perennial that grows in abundance along roadsides and old home sites. Giant hogweed, Heracleum mantegazzianum, 15 feet tall member of the carrot family introduced from Eurasia. Its sap can cause blisters so it is listed as a federal and PA noxious weed. Dame's-rocket, Hesperis matronalis, introduced from Europe to American gardens, now common in low woods floodplains and roadside ditches throughout PA. Yellow flag iris, Iris pseudacorus, is a showy ornamental plant commonly found in wetlands, along pond edges, and other wet areas where it can dominate. Moneywort, Lysimachia nummularia, goes by many common names and was introduced into the U.S. from Europe as an ornamental groundcover. Purple loosestrife, Lythrum salicaria, a European perennial with a woody base that has escaped gardens and destroyed large areas of waterfowl habitat by dominating wetlands and excluding all other plant life. Star-of-Bethlehem, Ornithogalum nutans and O. umbellatum, garden bulbs from Europe that escape to infest lawns and roadsides. Japanese pachysandra, Pachysandra terminalis, is an evergreen perennial groundcover that can spread from cultivation into natural areas if left uncontrolled. Wild parsnip, Pastinaca sativa, a European import now a widespread and abundant weed of roadsides throughout PA. Beefsteak plant, Perilla frutescens, a member of the mint family introduced from India now occasionally found in moist shaded roadsides and woods. Bristled knotweed, Persicaria longiseta, is an annual plant from Asia that can dominate wet, disturbed habitats. Japanese and Giant knotweed, Fallopia japonica and F. sachalinensis, are extremely difficult weeds to control. Imported from Japan they dominate stream and river banks throughout PA. Lesser celandine, Ranunculus ficaria, an aggressive weed in wetlands imported from Eurasia.
Carolina fanwort, Cabomba caroliniana, is a submerged, rooted plant native to the southeastern U.S. and sold for aquariums. Didymo, Didymoshenia geminate, is a microscopic alga called a diatom. It can form dense mats that smother stream beds and native vegetation. Brazilian water-weed, Egeria densa, is a popular aquarium plant that can grow vigorously and choke out native vegetation once it reaches ponds, lakes and other waterbodies. Hydrilla, Hydrilla verticillata, is a submerged aquatic plant that resembles several other aquatic plants, making ID difficult. Floating Primrose-willow, Ludwigia peploides ssp. glabrescens is indigenous to slow-moving waters of the southeastern U.S. now found in across southern PA. Parrot feather watermilfoil, Myriophyllum aquaticum, is an aquarium plant native to South America that can form dense mats in PA lakes and ponds. Eurasian Water-milfoil, Myriophyllum spicatum, a common an abundant Eurasian invader of lakes and rivers throughout PA. Curly pondweed, Potamogeton crispus, an aggressive European weed common in lakes, ponds and streams. Water-chestnut, Trapa natans, a locally abundant Eurasian invader of ponds and lakes. Narrow-leaved cattail, Typha angustifolia, is from Europe and difficult to visually distinguish from our native cattail.
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