How are weeds spread?

Here are a few ideas.

Do you ever get seeds stuck in your socks? They could be sharp grass seeds, or bristly thistles, or cockleburs (they look like footballs with needles). Dogs, sheep, and other hairy animals also carry the seeds from the wild and bring them to your house. Also birds leave undigested seeds in their droppings.

The bull thistle came from Europe and Asia with other good seeds to be planted for food.

We can prevent spreading weeds in good seed by having seed cleaned before planting. When buying plant seed see the certification for cleaning. You do not want to plant weeds.

List all the ways that seeds can be spread.

Bull Thistle - Asteraceae
(Sunflower Family)
Class B Weed

Bull thistle is a biennial. It takes two years or growing seasons to grow and make seeds It grows two to five feet tall in its second year. It has a long, fleshy taproot like a dandelion. Stems are very hairy and have dark purple veins. The first year’s leaves form a rosette and look like the musk thistle. Second-year leaves are double-toothed ending in a spine; are wavy; have prickles on the surface; and are hairy on the underside. Flower heads, made up of dark purple flowers, are 1.5 to 2.0 inches wide. Seeds are topped with a pappas.