Tree, perennial woody plant with an erect main stem - the trunk. More detailed and clear definition of this "life form" are difficult to give because of the variety of size and appearance of plants, called trees. Even a banana, for example World Tree Publications, is often considered a tree, although he stem herbaceous. Sometimes the definition of a tree specially emphasize that the trunk is divided into finer and finer branches, or that the tree has a clear leafy crown. However, the trunks of most palms do not branch, and the giant cactus lignified trunk, if and bears lateral branches, no foliage is not crowded.
Many definitions set the minimum height of the plant, which can be called a tree, but different authors, it ranges from 2 to 6 m. Sometimes this life form is attributed to the species, and in other cases only certain instances of a particular taxon. So, creeping plants in the high mountains or the Arctic can be called trees, as under more favorable conditions, the representatives of this species are erect and quite high. In other cases, the plant does not exceed a height of several decimeters, for example in the nursery or dwarf ornamental form created by the school of bonsai, but on all other grounds corresponds to a tree. All instances corresponding to a Mature state classic tree, begin their natural progression from a seed or tiny seedling vegetative. In this regard, the question arises: at what point they can be considered trees.