Tree houses are cute and nostalgic. Kids love them. But can they really provide a sophisticated luxury resort experience that’s worth returning to again and again? From Tennessee to the Loire Valley, five-star tree house resorts are popping up just about everywhere these days. A world-weary, been-there-done-that traveler might be tempted to dismiss the category of tree house hotels as just another novel, flash-in-the-pan Instagram moment. But a new generation of hoteliers begs to differ, claiming that ‘Gramability’ can coexist with the important work of elevating eco-consciousness.