Canada Thistle (Cursium arvense) (L.) Scop. (Asteraceae)
Photo from: http://www.arc.ab.ca/crop/weed/Weed.html#CARV, Dr. Alec McClay,  Crop and Plant Management Unit Biological Control of Weeds using Insects and Mites, Alberta Research Council, Vegreville, Canada.

Field Bindweed  (Convolvulus arvensis)
Field bindweed (Convolvulus arvensis) growing on an old railroad bed turned ranch road
near Cardwell, MT.  6/28/00.  Photo by T. Breitenfeldt.

WhiteTop (Cardaria draba)
 In Whitehall, MT.  Jefferson Co.  Photos by T. Breitenfeldt.

Leafy Spurge (Euphorbia esula L. )
Leafy spurge plants in the parking lot of Whitehall High School, Whitehall, MT.  Jefferson Co.  The plants were brought in with dirt for the parking lot and are pulled each year. Photos by T. Brietenfeldt.

 Russian-knapweed (Centaurea repens L.) (Acroptilon repens),  Asteraceae.
Last years seedheads sticking up above this years sprouts from roots. 6/01.  Jefferson Co., MT.

 Spotted knapweed  (Centaurea maculosa)
A spotted knapweed plant growing in the parking lot of Whitehall High School.  The seed came in with fill dirt for the parking lot.  The plant had been mowed several times and was hand pulled, bagged and disposed of right after this picture was taken. Photos by Todd Breitenfeldt, WHS science teacher.

http://mtwow.org/diffuse-knapweed-ID.html

Diffuse Knapweed (Centaurea diffusa) (Lam.)
Photo by Ron Lang, USDA-APHIS-PPQ.

Dalmation Toad Flax (Linaria dalmatica)
Flowers and leaves.  Photos by Bob Richard and Rich Hanson, USDA-APHIS-PPQ.

http://mtwow.org/Hypericum-perforatum.html

St. Johnwort (Hypericum perforatum)
Photo by Rich Hansen, USDA-APHIS-PPQ, Gallatin Co., MT. 

bloom

Sulfer Cinquefoil (Potentilla recta)
 Photo provided by the Montana Weed Control Association.

http://mtwow.org/common-tansy.html

Common Tansy  (Tanacetum vulgare L.)
pictures by: Jiasuey and Allaire, Wellestey College. .

dyers woad (Isatis tinctoria )
Photo by Ron Lang, USDA-APHIS-PPQ, UT. 

(Lythrum salicaria) purple loosestrife
Photo by: Bob Richard, USDA-APHIS-PPQ.  Location: Yellowstone Co., MT. 

Orange Hawkweed  (Hieracium aurantiacum L.) 

houndstongue (Cynoglossum officinale L.)
http://mtwow.org/houndstongue-plants.html

tall buttercup - (Ranunculus acris L.)
Photo from Montana Weed Control Association.

Tamaricaceae [salt cedar] (Tamarix ramosissima)
Photo by Ron Lang, USDA-APHIS-PPQ.  Location: WY.

http://mtwow.org/yellow-star-thistle.html

yellow star thistle (Centaurea solstitialis)
Photo by USDA-APHIS-PPQ. 

common crupina (Crupina vulgaris)
Pictures courtesy of: http://splash.metrokc.gov/wlr/lands/Weeds/crup.htm