What abundant Isle Royale shrub produces maple-like leaves, large white -petaled flowers and red, juicy, shower cap-shaped fruits? Why, thimbleberry, of course! If thimbleberries taste too tart to you, fruits of other island shrubs (blueberries, raspberries, and sugar plums) offer a sweeter alternative. When sampling island berries or other plant parts, make sure that you know what you are eating is safe; some fruits and plants are poisonous.