How to Identify Weed Plants


Any plot of earth, no matter how well-tended, has the potential of turning into a weed patch almost overnight. This is because weeds, like rabbits and other garden pests, propagate rapidly. Dormant seeds may hide in soil. Creeping stolons and decapitated taproots may send up new plants. Worst of all, grassy or broadleaf weeds may overrun a thin, undernourished lawn. Weeds are aggressive and overbearing. They kill desirable plants and grow where they are not wanted. There are thousands of weeds, and the wise gardener enlists some help in identifying them.

Step 1

Keep records of what you plant and what was there when you began your garden or lawn so you know what plants belong. Odd plants that suddenly spring up and spread rapidly may be invasive weeds that will strangle more refined lawn and garden plants.

Step 2

Find weeds in your own yard or partner with a neighbor to start a neighborhood inventory. Crabgrass, an annual weed, and quackgrass, a perennial, are common grassy weeds. Horseweed and chickweed are common broadleaf weeds; tall horseweed resembles several garden plants, including phlox and chickweed, and has delicate white flowers borne on vines of heart-shaped flowers. Common purslane is another broadleaf weed; it has red stems and succulent-type leaves that spread on hot, dry soil and choke out stressed lawns and gardens.

Step 3

Learn the difference between a native plant and an invasive weed. The University of Illinois extension lists several surprising weeds including phlox, wild violets, yews and yucca. Each grows aggressively, choking out wildflowers and other native plants. University extensions and organizations like the Lady Bird Johnson Wildflower Center maintain native plant databases.

Step 4

Trade information with other gardeners on your block and in your area. A plant that stumps you may be an old adversary for a neighbor. Local garden center merchants know what weeds customers are trying to eradicate.

Step 5

Take a walk through the neighborhood with your digital camera and take pictures of plants that appear to be taking over in lawns and gardens. Identify them using materials published by agricultural research stations, state integrated pest management (IPM) organizations and university extensions. Assemble a gallery of photos to use to identify weeds. Add new weeds as you find them to create your own reference for your area.

Tips and Warnings

  • When hunting really bad weeds, arm yourself with long sleeves, long pants and garden gloves; Canada thistles’ hairy leaves are particularly irritating, purple loosestrife is banned in dozens of states, and poison ivy’s three-lobed leaves contain oils that inflame skin. Your city’s forester or weed commissioner can tell you which weeds are the worst offenders and provide information. Identify before digging. Precious native plants like trillium, columbine and other wildflowers have faced extinction because they were dug up as weeds.

Things You'll Need

  • Notebook
  • Digital camera
  • Memory device; CD or prints for notebook


  • University of Illinois Agricultural Extension Services: Weed Identification
  • Connecticut Agricultural Experiment Station: Identifying and Managing Weeds in Gardens
  • Grounds Magazine: How to Identify Weeds

Who Can Help

  • Lady Bird Johnson Wildflower Center: Native Plant Database
  • Virginia Tech Cooperative Extension: Weed Identification Guide
  • Rutgers New Jersey Agricultural Experiment Station: Weed Gallery Thumbnail Photos
  • Weed Science Society of America: Photo Gallery
Keywords: identify weed plants, noxious invasive weeds, integrated pest management

About this Author

Chicago native Laura Reynolds has been writing for 40 years. She attended American University (D.C.), Northern Illinois University and University of Illinois Chicago and has a B.S. in communications (theater). Originally a secondary school communications and history teacher, she's written one book and edited several others. She has 30 years of experience as a local official, including service as a municipal judge.