angles building cascading city creepers ecological ecology edge edges edging environmental gardening gardens green greening hanging height high highrise plantings plants rooftop safety Singapore trees trimmed trimming urban vertical vertical-gardening vertical-gardens vines wall-garden worker Begonias bromeliads cloud-forest color colorful colors colour colourful conservatory decorative delicate-ferns dense density distinctive dome epiphytic ferns flora flowers foliage greenery greenhouse leaves lush-vegetation orchids tropical-highlands tropical-mountains balconies balcony cutting gardener ladder man pruning safety-harness secure above-ground architectural architecture danger dangerous elevated futuristic Gardens-by-the-Bay iconic icons landmarks panoramic panoramic-vistas reinforced-concrete scenic skyline steel strong Super-trees Supertree-Grove suspended tree-tops views vistas aerial-walkway cables connected connections OCBC-Skyway pedestrians stroll strolling walkway