Possible Clues:

• Track to follow round peaks where fruit grows
• Fruit plantation
• Old park-keeper, Head of Yeovil Conservatory
• Greenhouse for a certain citrus fruit
• Hothouse's coloured lines
• Park-keeper visiting old Yankee where fruit-trees grow
• 'Greenhouse gas discovered in NY. Roger. Out.'
• Men cross about Spain being hot place to grow fruit
• Men furious earl's broken into hothouse
• Glasshouse perhaps more colourful by end of July