Knapweed, Spurge and Toadflax type Differences
Leafy Spurge (Euphorbia esula). Broken stems ooze a sticky white latex sap (don't get this sap in your eye as it can damage eye tissue).
See pages 13, 20-23 in the following FS document for descriptions of other types of spurge.
http://www.fs.fed.us/foresthealth/technology/pdfs/LeafySpurgeBiocontrols.pdf
Dalmatian Toadflax (Linaria dalmatica) has wide waxy leaves and beautiful snapdragon flowers.
Yellow toadflax (Linaria vulgaris) has thinner leaves than dalmation, flowers are smaller, but similar.This plant is also known as butter and eggs.
Diffuse Knapweed has white flowers (very rarely purple) and has sharp tipped bracts (bracts are the scales around the seed head).
photos of spurge, toadflax and diffuse knapweed by USDA APHIS
Spotted Knapweed has purple flowers (very rarely white). Bracts are not sharp tipped and are fringed in black giving the seed head a spotted appearance.
Russian Knapweed also has purple flowers. Bracts are not fringed in black and have transparent tips-- go to the following link for several pictures.
http://calphotos.berkeley.edu/cgi/img_query?query_src=photos_index&where-taxon=Acroptilon+repens
Squarrose knapweed, Brown, Black and Meadow knapweeds all look very similar to Spotted knapweed. For information on telling the differences see pages 7-13 of: