Network Center masthead with Musk Thistle.
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THE ENEMY: Bull thistle (Cirsium vulgare)

Strategy: This non-noxious, biannual invasive weed can be found throughout Idaho. It has very hairy leaves that are deeply lobed. It generally only reached a height of 4 feet. The plant produces a oval shaped flower bud with pink pedals that are about the size of golf balls. This is contrast to Musk thistle which has a flat shaped flower and is consistent to the size of a baseball and can grow to 6 feet in height. Bull thistle can be found in lawns, pastures, agricultural crops, and disturbed areas. It is non-toxic but is very undesirable as it grows spines on the entire plant.

Attack: This thistle is very competitive as it grows in areas of stiff competition. Many livestock animals will graze on the thistle especially when the plant is in the full bloom stage. Its rosettes can grow to a diameter of 24 inches and can choke out the beneficial plants. The seed has a large plume that allows it to drift in the air and travel long distances before it plummets back to the ground and into the waterways to start a new infestation.

Defense: Since this plant is a biannual, mechanical control can be effective. Minimize your disturbance by digging around the plant with a shovel then pull the plant out from the ground with a gloved hand. If you are going to revegetate the site then you can use a plow or disc to remove the weed. 2,4-D is an effective herbicide as long as you treat the weeds early in the spring. Once the plants send up the vegetative growth one needs to switch to Telar XP, Escort XP, Milestone, Opensite/Chaparral, or even Tordon 22K. Consult with your weed professional such as your County Weed Superintendent.

7/12/17
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