Per the Wild Resources Conservation Program's Dangerous Invasions DVD (copyright 2007) there are about 100 highly invasive plants in PA.

Invasive plants have the ability to reproduce rapidly, spread over large areas, and lack such natural controls as herbivores and diseases to keep them in check. Help maintain our biodiversity of native plants and creatures by removing invasive plants from your property and replacing them with native plants.

Alternatives

Alternatives to invasive or potentially invasive exotic plants

New England Wild Flower Society by William Cullina. Text only.

Plant Invaders of Mid-Atlantic Natural Areas

National Park Service

U.S. Fish and Wildlife Service

Click on any invasive plant in the list to view plant photo and detailed information. Scroll to bottom of plant info to view list of alternative native plants to grow. Be sure alternative plant is appropriate for your site, i.e., moisture, light.

Identification 

Invasive Exotic Plants in PA List

PA Dept of Conservation and Natural Resources, DCNR. Scroll down page to view list by scientific and common names and to click on links to Fact Sheets with excellent photos and Management & Control measures with most plants.

Mistaken Identity: Invasive Plants and their Native Look-alikes--an Identification Guide for the Mid-Atlantic

Pub by Delaware Dept of Ag, Nov 2008. Full-color, 62-page booklet. The purpose of the work is to facilitate correct identification of confusingly similar invasive and native plant species. Targeted at land managers, gardeners, conservationists, and all others interested in plants, this booklet covers over 20 invasive species and their native look-alikes. 

Invasive Plant Atlas of New England

Joint project of The Bugwood Network, USDA Forest Service and USDA APHIS PPQ.The University of Georgia - Warnell School of Forestry and Natural Resources and College of Agricultural and Environmental Sciences - Dept. of Entomology

In left column click on "Catalog of species", then choose specific common or scientific name to search for plant info. At plant info page, click on scientific name to obtain full text and photos; be sure to scroll down for all photos and text. Some plants are only searchable by the scientific name. Click on  photos for closeup views. No alternatives given.

Invasive Plants of the Eastern United States: Identification and Control 

Joint project of The Bugwood Network, USDA Forest Service and USDA APHIS PPQ. The University of Georgia - Warnell School of Forestry and Natural Resources and College of Agricultural and Environmental Sciences - Dept. of Entomology  Full text/photos.. Includes Aquatic Forbs, Ferns, Forbs, Grass/Grass Like, Shrubs, Trees, Vines, Publications, Project Information. Scroll down page to all links. Another means of searching similar info in Invasive Plant Atlas of New England source noted above. CD available at Union County Ext. office and The Public Libraries of Union County.

Plant Invaders of Mid-Atlantic Natural Areas

Publication by USFWS BayScapes Conservation Landscaping Program

Click on any invasive plant in the list to view plant photo and detailed information. Scroll to bottom of plant info to view list of alternative native plants to grow.

Invasive Plants

Indepth info through various sites of the New England Wild Flower Society. For invasive plant photos click on their Photo Gallery. At the photo link click on any photo for an enlarged version of the photo as well as information.

Invasive Plants: a guide to Identification and the Impacts and Control of Common North American Species by Sylvan Ramsey Kaufman and W. Kaufman, Stackpole Books 2007.

Control Measures

Scroll down this page to see info under Specific Invasive Plants.

Search engines for control measures:

Invasive Exotic Plants in PA List - PA Dept of Conservation and Natural Resources, DCNR. Scroll down page to view list by scientific and common names. Link to Management & Control measures are in right hand column.  

Biological Control:A Guide to Natural Enemies in North America - Cornell U. guide to biological controls of insect, disease, and weed pests.

Control of Invasive Non-Native Plants: A Guide for Gardeners and Homeowners in the Mid-Atlantic Region - MD Native Plant Society, 1999.

The Invasive Species Alien Handbook - MD Native Plant Society, useful summary for ID and removal of common invasive alien species; English Ivy, Garlic Mustard, Japanese Honeysuckle, Japanese Stillgrass, Multiflora Rose, Tree of Heaven, and Wineberry; sketches, photos, text.

National Invasive Species Info Center - USDA Current Invasive Species News.

Specific Invasive Plants (just a few)

Garlic Mustard, Alliaria petiolata

First recorded in the U.S. around 1868 in Long Island, NY; thought to have been introduced by settlers for food and medicinal purposes.

Member of the mustard family, Brassicaceae.

Biennial plant meaning the first year it is a seedling with a basal rosette. The second year it flowers and sets seed.

Grows in a wide habitat range from moist to dry. May be aided by white-tailed deer since they prefer eating native wildflowers rather than garlic mustard. Able to tolerate low light areas.

A single plant may produce hundreds of seeds which may be viable for more than 5 yrs.

MI State U

Giant hogweed, Heracleum mantegazzianum

Imported from Eurasia around 1917 as an ornamental plant.

Member of the parsley family, Apiacea,  grows 8 - 14 ft.

It is a dangerous, poisonous plant. Do not touch it as it  produces a toxic sap which when exposed to sunlight may cause burns on your skin. 

If you find this plant on your property call the Dept of Ag's Giant Hogweed Hotline 877.464.9333 to handle control measures. Leave a daytime phone number to be contacted in a few days.

PA Dept. of Agriculture - link to PDF brochure, excellent photos and brief, informative text.

Cornell U. 

DCNR

Japanese Knotweed, Polygonum cuspidatum

Native to Japan, introduced into North America for ornamental use in the late 1800's. Extensively planted at strip mine reclamation sites in PA.

Member of the Buckwheat family, Polygonacea, may grow over 10 ft.

Extremely difficult to control because it aggressively spreads by stout rhizomes which may reach 65 ft. in length and readily regrows from vegetative pieces and seed.

Invasive Plants of the Eastern U.S.  

Invasive Plant Atlas of New England  

PA Flora - Botany Department, Morris Arboretum of the University of Pennsylvania; excellent photos, sketches,

Japanese Knotweed Alliance - Indepth info and detailed photos by CABI, a nonprofit international organization based in the United Kingdom.

Mile-a-minute vine, Polygonum perfoliatum

Probably established on east coast by unintentional introduction in 1930's in York County, PA.

Recurved barbs on reddish stems and underside of leaf blades.

Smothers plants and trees in meadows, forest edges, and wetlands. Limited photosynthesis in the smothered plants can eventually kill the plants.

DCNR

Multiflora Rose, Rosa multiflora

Multistemmed, thorny shrub introduced to East Coast from Japan in 1866 as rootstock for ornamental roses. In 1930's used for erosion control  and as a "living fences"to contain livestock.

DCNR   WeedUS

Purple loosestrife, Lythrum salicaria

Brought here from Europe in the 1800's for ornamental and medicinal uses.

Quickly spreads in wetlands killing off native plant species.

DCNR

Galerucella calmariensis and G. pusilla  European beetles introduced in US in 1992, detalis Biological Control:A Guide to Natural Enemies in North America

Tree of Heaven, Alianthus altisima

Introduced by a gardener in Philadelphia in 1784 and into CA by immigrants during the gold rush era.

Can produce 325,000 seeds per year which thrive in disturbed soils.

DCNR

Other Resources

UD researchers study impact of alien plants on native insects - Doug Tallamy, UDE; 7.3.07.

UD scientist fears insect food supply affected by non-native plants - Doug Tallamy, UDE; 8.2.01.