Possible Clues:

• Potato or yam?
• Drive a coach and horses through raised part of the vegetable garden
• Yam or cassava, for example
• Yam or rutabaga
• Jerusalem artichoke or jicama, e.g
• Knob in brass instrument mentioned
• Rutabaga, e.g
• Root of trouble started by transport company
• Satsumaimo or taro
• One floating down a river or speeding down a snowy slope