Thistle weed is a noxious, undesirable pest that spreads quickly in a garden and requires determination and persistence to eradicate. This deep-rooted weed has small flowers that appear beautiful in the beginning, but become a gardener’s worst nightmare with the passage of time. It competes with desirable plants for food and water in the soil, thus depriving them of essential nutrients. Although there are several methods of ridding your lawn from this weed, eradicating it completely requires a combination.
Mow your lawn grass, including thistle weed, down to up to 2 inches just before the onset of winter. This is effective for large infestations of thistle, as they do not have time to recover by the time winter arrives, and freeze out in the cold.
Dig out thistle plant by hand or with a small shovel before flowering, if there are a few in your yard or garden. Dig deep around the plant to get all the deeply embedded taproots to prevent the plant from growing again. Collect in a bag, knot it firmly and discard.
Spread a large plastic sheet, tarp or deep colored, heavy fabric over the thistle plant to prevent sunlight from reaching it. This is effective for small thistle infestations that die within weeks because of no contact with air, sunlight or water.
Allow grazing cattle such as goats and cows into areas with large thistle infestations such as pastures or green lands. These animals pull the thistle from the ground and eat it.
Introduce thistle-eating insects such as thistle-head weevil, thistle-stem gall fly and thistle rosette weevil to areas with large infestations. Thistle head weevil lays eggs on the flower heads and the larvae feed on the seeds, preventing them from dispersing. The thistle rosette weevil kills rosettes to prevent the growth of older plants. The gall fly bores into the stem of a thistle plant and causes a gall.