Evergreen plants have leaves or needles that stay on the plant through out all of the seasons. This does not mean that the needles or leaves never die or fall off. It means that when they do, they are replaced by new ones and the plant is never without greenery, although you will not get the change of colors in the fall. There are basically three types of evergreen plant. The first one includes needle and broadleaf plants that can be found in all areas of the country such as members of the holly, pine and spruce families. There are also plants like vines and flowering plants that are evergreen in the warmer areas, but deciduous in the colder north. The third group consists of tropical and semi tropical plants that only grow in the warmest areas such as palm trees.
Deciduous plant loose all of their leaves for part of the year. The leaves of most deciduous plants turn color in the fall. Actually, the color in the fall is their real color. They are green the rest of the year because of the presence of chlorophyl. Once the cool weather comes and the plant starts to go dormant for the winter, there is no more chlorophyl and the leaves become their real color. During the winter, when the tree does not have to worry about keeping the leaves green, it devotes its energy to storing up the nutriments the new leaves will need in the spring. In the warmer areas, it is not winter that causes the change, it is the dry season.
Semi-evergreen can mean different things. It can refer to plants that loose most of their leaves in the fall or during dry periods, but still keep some of them. It can also refer to plants that keep all of their leaves into the winter and then loose them as compared to trees that loose their leaves in the fall. Then again, there are trees who keep dry leaves all the way through the winter until the following spring, but calling them semi-evergreen is stretching things just a bit. Still again, there are trees that will be evergreen in the south, but semi-evergreen in the north.
Is one type better than the other? It depends on many thing, including what you are looking for. When deciduous plants loose their leaves, they conserve their energy, nutrients and water. Losing leaves also minimizes the damage from insects. Evergreens, on the other hand, loose nutrients and water during the winter. Of course, the main consideration is what is hardy in your area. Make sure you plant the trees in the sun conditions and type of soil they need. Each one needs something different and non matter what one you choose, if you take care of it right, it will turn out the way you want it too.
New World Encyclopedia