Possible Clues:

• Post-harvest stalks
• Transport a thousand bits and pieces left after harvesting
• Surprise university master with potato stalks
• What's inside German city? Stalks!
• Pull up by the thousand potatoes below this
• Bedding material in transport on motorway
• Start to pull this to get it grand over your potatoes
• Thatching stalks
• Stalks maiden on trail
• Pull a thousand over the potatoes