Welcome to the “Weed Web site” at Penn State University. As you know, weeds can be native or alien invasive plants that harm agricultural, disturbed, and natural ecosystems. Some people call weeds “plants out of place”, but to farmers, conservationists, land managers, and even homeowners, weeds can be extremely problematic.
Publications and Resources are available from Penn State’s College of Ag. Sciences Publications Distribution Center. To order, call (814) 865-6713 or visit your local Penn State Cooperative Extension office.
This photo gallery contains pictures of many plants that are common to North America. Some of the plant species listed are not generally considered weeds but may have toxic or poisonous properties, or are otherwise of general interest as wildflowers or herbs.