Possible Clues:

• Forest keeper invested in only coreless fruit source
• Hothouse containing citrus fruit
• Building in which citrus fruits are grown
• Soldiers endued with temper ultimately qualify for the glasshouse
• Basho's last lines about region where mandarins thrive
• Empty-headed boy hides Rover in the greenhouse
• Golden year pursuing passion fruit here
• Plant-house
• Place for growing fruit in cool climates
• First off, lad traps park keeper in greenhouse, maybe