Evergreens


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Evergreens

 

plants covered with green leaves all year round. Some leaves are shed and others reappear. In addition, each leaf separately may sometimes live as long as several years. In tropical countries, evergreens predominate. There are also many in the subtropics (for example, laurel, oleander, olive, magnolia, fig, and certain oaks). The following are classified as evergreens in zones of temperate or cold climate: conifers (except larch), semishrubs (mainly from the Ericaceae family; heather, bilberry, cranberry, and so forth), and certain grasses (such as asarabacca and pyrola) that survive the winter under the snow. Grassy plants (such as winter weeds, winter cereal grains, and certain sedges) are not classified as evergreens, since they are either winter annuals or perennials in which the shoots that have survived the winter die in the spring and are replaced by newly developed ones. In temperate zones, photosynthesis in evergreens is suspended during the winter. Instead of starch, sugar or oil is formed in the leaves; this promotes an increase in the hardiness of the plants. The chlorophyll partially decomposes, leading to some browning or even reddening of the needles in many conifers (for example, thuja and cryptomeria). Respiration in evergreens is reduced in winter; in the spring, the active life processes are resumed.