Conifers

• Familiar in the United States as the ubiquitous Christmas tree, conifers are evergreens with distinctive, needle-like leaves. Conifers range in size from tiny shrubs to the giant sequoia, the largest living entity on Earth -- and one of the longest lived. Conifers resist extremes of heat and cold by limiting the amount of moisture lost through their leaves, coated with a thick, waxy cuticle. Many also grow in a conical shape that helps them shed snow during the winter.
  
  

Rainforest Trees

• Unlike conifers, most evergreen broadleaf trees grow in areas where temperatures do not drop below freezing, like tropical rainforests. Because these trees do not need to go dormant during the cold season, they have no need to drop their leaves. These trees grow to different heights, with the tallest reaching 120 feet, a second layer at about 80 feet and a third layer at 60 feet. The tallest trees have small leaves to minimize evaporation in the strong sunlight, while shorter trees have large leaves to catch as much light as possible after it filters through the top layer of foliage.
  
  

Live Oak

• Live oak is native to coastal areas of the southern United States, where it grows in swamps, forests, sandy areas and on barrier islands, with temperatures that generally do not fall below freezing. The tree, which has several twisting columns forming the trunk that spread out into three to five arching branches, is tolerant of salt spray and low moisture, though it remains dwarfed in very dry areas. Live oak produces a crop of 1-inch-long acorns almost every year, providing a valuable source of food for wildlife.
  
  

Cycads

• Cycads are ancient plants compared to most common trees that live in temperate areas. Consisting of a thick, central column -- often covered with scaly bark -- with palm-like leaves growing from the top, cycads are often used in landscaping large indoor areas like shopping malls, where they are not exposed to extremes of temperature. Most cycads are difficult to propagate, requiring growth from seed and taking years to reach transplant size. Sago palm is the exception, since it can be propagated vegetatively, through cuttings.