Canada thistle

1. Canada thistle • Scientific name: Cirsiumarvense • Family: Asteraceae • Life cycle: Perennial • Where found: Range, Cropland • Physical description: • Seed: light brown, 3-4mm long, with feathery white plume • Cotyledon: oval to oblong, visible white midvein • True leaves oval to elliptic in shape, with dentate to deeply pinnate margins • Forms a basal rosette at first, then alternate when flowering • Leaves sessile; prickly and spine-tipped with a waxy surface • Purplish-pink flowers less than 2.5cm across • Interesting facts: • Primarily reproduces by extensive creeping rhizomes • the only rhizomatous thistle • Female flowers have a pleasant, vanilla-like aroma • Latin name describes distinct midvein of leaf • Cirsium = swollen vein

2. Field bindweed • Scientific name: Convolvulus arvensis • Family: Convolvulaceae (Morning Glory family) • Life cycle: Perennial • Where found: Range, Cropland • Physical description: • Seed: dark grey to reddish brown, three-sided • Cotyledon: linear to oblong • True leaves heart-shaped becoming arrowhead-shaped • Often confused with wild buckwheat • Similar leaf shape, arrangement alternate, petiolate leaves • Nodes of wild buckwheat have papery sheath, absent on field bindweed • Wild buckwheat has inconspicuous flowers, field bindweed has large white-pink, funnel-shaped flowers • Wild buckwheat leaf bases point in, field bindweed bases point outward • Growth habit: climbing/creeping, rhizomatous • Interesting facts: • Will host viruses affecting potatoes and tomatoes Wild buckwheat Field bindweed

3. Weed Management Techniques

4. Prevention • Cultural • Mechanical • Biological • Chemical

5. Questions! • Crop scouting is considered a preventative control. True or False? • Which of the following types of weed management is currently the least effective? • Cultural • Mechanical • Biological • Chemical • Is mulching an example of mechanical weed control? Why or why not?