Spiny weed

Asked September 7, 2013, 2:00 AM EDT

My mom found a batch of these weeds in her pasture. What are they? How do we kill them!

Douglas County Oregon weed issues horticulture

1 Response

Those are Distaff Thistle. Sometimes they are called Wooly Distaff Thistle. They are considered a type A designated weed in Oregon which means people are asked to eradicate them.
Your picture shows the thistle with seed heads and dried. If you can cut them carefully and collect them, then put them in a burn barrel or a place where they can be burned when the burning ban ends. You want to keep the seeds from dispersing if possible. This is an annual invasive weed which means you will see new seedlings next spring. Spray the seedlings when only a few inches tall and well before they go to seed. You can use any of these broadleaf herbicides. MCPA, Crossbow, Weedmaster, Curtail. Roundup will work too but it will also kill any grass or legume plants near them. Spraying annual plants late in the season , like this time of year, when they have seed heads wont kill the seeds.