Possible Clues:

• An elitist backing one form of 'potty' art
• Art of growing dwarfed trees
• Little growth in good French spoken � not to mention Deutsch
• Tree's fine after black wood's tips cut off
• Often-trimmed tree
• Potted tree or shrub artificially prevented from reaching normal size
• Very little tree
• One's a pretentious type about specialist arboriculture
• A snob climbing a first class sort of tree
• Literally, 'tray gardening'