Yellow foxtail, prickly lettuce and horseweed are just a few that may sneak into your garden or lawn in straw used as mulch.
From the washingtonpost.com
At another large farm, I saw melons, lettuce, asparagus, cabbage, broccoli, chard, collards, prickly pears, almonds, pistachios, grapes and more tomatoes than anyone could conceive of in one place.