Evergreens, trees that retain their leaves or needles and stay green year-round, play a large part in the lives of many people, though most don't often think of it. Without evergreen trees there would be no chocolate, coffee, corks for wine bottles, mangoes in fruit salad, chewing gum and no cinnamon or cloves to sprinkle on toast.
Avocado trees are mostly evergreen according to Diana Wells, author of "Lives of the Trees, An Uncommon History," but sometimes lose leaves for a short period depending on location. Other evergreens include the boxwood tree, cacao tree---which produces cacao beans, the source of chocolate---the China fir, cinnamon tree, clove tree, coffee tree, cork tree, cypress, sycamore fig tree, holly, Japanese cedars, Joshua tree, mango tree, neem tree, and strawberry trees, known commonly as madrone trees.
Evergreen Leaf Cycle
Though evergreens are often defined as simply holding their leaves or needles year-round, they do eventually regenerate, even if after a few decades. According to tree expert David Allen Sibley, author of "The Sibley Guide to Trees," evergreens may hold leaves for 12 months to 30 years, but two to four years is more common. Deciduous trees, in contrast, are defined as trees that lose all their leaves less than 12 months after they grow, and become bare and leafless for part of the year. Naturally, some trees are on the border of this definition.
Topiary, the art of sculpting trees and shrubs into recognizable shapes, dates from Roman times and almost always uses evergreens as its medium. Evergreens such as boxwood, bay laurel, myrtle, yew and privet are preferred for topiary because of their small leaves or needles and compact growth habits. Though the art was revived in Europe during the 16th century and has largely been associated with the European elite, it has bettered many gardens on both sides of the Atlantic.
Several evergreens are known to have healing properties. According to canopy biologist Nalini M. Nadkarni in her book, "Between Earth and Sky: Our Intimate Connections to Trees," Northern white cedar, which grows throughout the northern Midwest, is used by the Algonquin, who spread the branches on the floor of their sweat lodges and distill a tea rich in vitamin C from its scale-like leaves. White pine often grows a fungus on its roots, which the Chinese use as a sedative. Tamarack trees have been used by the Ojibwa to treat headaches, by crushing the leaves and bark, placing them on hot stones and inhaling the fumes. Pacific yew trees have produced Taxol, one of the most successful cancer drugs ever developed.
You may not think of evergreens when popping that piece of gum into your mouth, but it has more to do with trees than you think. According to canopy biologist Nalini M. Nadkarni in her book, "Between Earth and Sky: Our Intimate Connections to Trees," the ancient Greeks chewed a gummy substance called "mastiche," derived from the resin of the small evergreen mastic tree. In Central America, the Mayans collected chicle, the coagulated sap of the sapodilla tree, the raw material for what has since become the worldwide chewing gum industry.