Quercus

摘要

A genus of deciduous or evergreen trees, occasionally shrubs, Quercus, the oaks, is a member of the beech family, Fagaceae. It consists of some 600 species native to the Northern Hemisphere, extending from cold temperate to tropical regions. Two are native to the British Isles, Q. robur and Q. petraea, and both are synonymous with the English countryside.Oaks have spirally arranged leaves, many with lobate margins— the iconic leaf used as a logo by the National Trust—but some have serrated leaves or entire leaves with smooth margins. While many oaks produce tall majestic trees with broad spreading canopies where space allows, there are some that offer interest with a pyramidal or almost columnar habit. A single oak will produce both male flowers (catkins) and small female flowers. The fruit is a nut, the acorn, usually with a single seed. Autumn foliage can be breathtakingly spectacular.