Possible Clues:

• Couple starting off bright and early, both caught short, needing tree!
• Tree valued for its long-burning firewood
• Tree with bitter 'nuts'
• Deciduous tree with smooth grey bark
• Tree with prickly burs
• Wood from shore area we hear
• Source of mast that's come ashore, we hear
• Nut-bearing hardwood
• Wood in shore area mentioned
• Check under insect in wood