When you strew something, you scatter it all over the place. At a wedding, for example, the flower child's job is to strew the path with petals.
One of the scariest parts of The Wizard of Oz is when the winged monkeys pounce on the Scarecrow and strew his insides all over the forest floor. Strewn is a more common form of the word, as in “after the tornado, the farm was strewn with debris.”