Evergreen trees are plants that keep the garden alive, even in the cold, dreary months of winter. Evergreen trees are trees which retain their foliage year-round, rather than losing their leaves annually like deciduous trees do. There are a number of different types of evergreens, and some distinct advantages to being evergreen as opposed to deciduous. Many tropical trees are evergreens, and evergreens are also very common in temperate climates. In colder regions of the world, evergreens are more rare, but still present. From the tree’s perspective, being evergreen requires less work. Deciduous trees require a lot of energy and nutrients in the spring, when they put out new leaves. Evergreen trees, on the other hand, conserve energy and nutrients by slowly growing new foliage year-round, which can be an advantage in regions where nutrients are tight, as an evergreen can endure a rough season, while a deciduous tree might fail. The leaves also provide insulation for the tree, preventing sun and frost damage on the branches and trunk. Evergreens also fertilize themselves, thanks to their nutrient-rich leaf litter, which also acts as mulch to protect the roots.
Some evergreen trees grow new foliage constantly, with older foliage dropping off as it is displaced. Others have slower rates of growth, losing leaves only periodically. In all cases, the foliage remains green and crisp year-round, with paler growth being newer. In spring, for example, new growth can appear almost yellow next to the more mature foliage. Most evergreens have needle-shaped leaves, to conserve water, and many evergreens have slightly waxy foliage, which also helps to prevent evaporation through the leaves.