Zone 8

USDA Zone 8 is part of a classification scheme, originally drawn up by the US Department of Agriculture, of local temperature extremes as they affect plant hardiness. It associates places where the lowest winter temperature, averaged over several years, is to be found in a range of approximately -7 to -12 degrees Celsius. Most of Germany is a good deal colder in the wintertime, and nationally active German nurserymen are wary of any plants rated as not hardy enough for Zone 7. In Hamburg, winter temperatures below -12 degrees have occured very occasionally, despite the city's location astride a river estuary, but there are some indications that the Hamburg winters are now becoming milder, so I feel confident in this climatic classification. Many species recommended by plantsmen as hardy in Zone 8 have been proven to survive outdoors in Hamburg with appropriate care. The plants that do succumb to the Hamburg winters are those which are susceptible to winter damp, since Hamburg has a maritime climate and very cold weather in the city seldom lasts more than a week at a time. Hamburg gardens lack the benefits of continuous snow cover, which is said to insulate plant roots from very cold air temperatures. The city's cycles of freezing temperatures followed by rain thus often lead to root rot or weaken a plant's resistance to other fungal diseases. USDA zones may soon be on the way out. The American Horticultural Society is reportedly drawing up a new scale of 15 hardiness zones to replace the USDA 11.