Gardener and U.K. citizen Christopher Thacker goes on record in his book "The Genius of Gardening," as defining fast-growing trees and shrubs as those species that add more than 8 inches to their primary stalks and 6 inches to secondary branches every year for the first 5 years of their life cycle. They add 6 inches or more to both primary and secondary branches following that until the shrub or tree reaches maturity.
Native to both Scotland and Ireland, Ulex europaeus, or the common gorse, is an evergreen shrub that grows between 7 and 10 feet tall. It grows from a series of stalks rather than a central trunk. Only seedlings produce normal leaves. Older gorse produces a series of green spines sufficient for photosynthesis and range between 1 and 3 cm in length. They act to protect the pea-flower shaped, yellow blooms and leguminous seed cases from grazing animals.
The common hazel, or Corylus avellana, is a large deciduous shrub found ranging from the British Isles to northern Iran. It grows most effectively in cool, moist environments. Aside from being used in hedgerows, hazel are cultivated for hazelnuts, which grow in clusters of one to five and have husks encasing ¾ of their lengths. Each specimen can grow up to 25 feet high unless kept pruned. Its leaves range between 3 and 6 inches long, have rounded backs, hairy tops and bottoms that are dark red in color and double-serrated ends. The flowers are yellow and bloom before the leaves grow in early spring, each a long, streamer-like formation called a catkin.
European privet, Ligustrum vulgare, is the only species in the privet genus native to the United Kingdom. It is classified as a semi-evergeen in that its leaves do not fall off during winter and are similar to needles in appearance and shape. Privets grow up to 9 feet high and have woody, gray branches with brown spots called lenticels, which act as part of the shrub's vascular system. The leaves always grow in pairs, are oval in shape, pointed and measure roughly 1-1/2 inches long by 1/2 inch at their widest. The fruit the European privet produces in mid-summer is mildly poisonous to humans and mammals, although it does no harm to songbirds that it relies on to spread its seeds.