Possible Clues:

• Big-head, in state of elation, found in the garden
• Elation finding first bud in flower
• Covering top of bush, a high plant
• Fear of Brussels closing region's chief plant
• Plant finds bachelor in high spirits
• Ecstasy, barbiturates, at first hidden in shrub
• Transport seen around British plant
• Bush perhaps began in excessive optimism
• Growth of intoxication with British coming aboard
• Joy when bee's invaded that plant