Ground ivy. Photo provided by: Leslie J. Mehrhoff, University of Connecticut, Bugwood.org.

Canada thistle. Photo provided by: John M. Randall, The Nature Conservancy, Bugwood.org.

Close-up of Canada thistle leaves. Photo by: Leslie J. Mehrhoff, University of Connecticut, Bugwood.org.

Dandelion. Photo provided by: Howard F. Schwartz, Colorado State University, Bugwood.org.

Dandelion seedlings. Photo provided by: Joseph M. DiTomaso, University of California – Davis, Bugwood.org.

Clover. Photo provided by: Howard F. Schwartz, Colorado State University, Bugwood.org.