Q How can the famous English gardens grow so well with the cloud cover that always seems to be hanging over them?
A "Contrary to popular myths, England is not constantly shrouded by rain clouds," said Mr Rowan Blaik, the director of living collections at the Brooklyn Botanic Garden.
As for the hours of solar radiation needed to power photosynthesis, the Met Office, Britain's government weather and climate recorders, keeps a national record of sunshine hours, he said.
Its most recent long-term average climate data, spanning 1981 to 2010, found a considerable range of sunshine durations.
Ventnor Botanic Garden on the Isle of Wight, just off the south coast of England, received a long-term daily average of 8.3 hours of sunlight in July, compared with 5.4 hours for Cragside, Northumbria, in the north-east.
Britain has one big advantage in that it has only one climate zone, temperate, which is ideal for growing plants, Mr Blaik said.
This is especially fortunate as the United Kingdom as a whole has just over 1,400 native plant species.
Plant introductions from other temperate zones around the world helped give the nation such a rich horticultural history, he said.
Mr Todd Forrest, the vice-president for horticulture and living collections at the New York Botanical Garden, agreed that for much of Britain throughout the year, climate conditions are ideal "for a remarkable range of temperate-zone garden plants".