A tree sapling is an immature tree with a slender trunk. Depending on the species of tree, a sapling can be between three and 15 years old, and range in height from 2 to 10 feet (about 0.61 to 3.05 m). Saplings differ from seedlings, which are trees that are less than three years old. The principal attributes of a tree sapling, aside from its age, are trunk flexibility and smooth bark; mature trees generally have thicker, darker outer bark. Ordinarily, saplings do not produce fruit or flowers.
In most cases, the best stage at which to plant a tree is when it is a sapling. Seedlings, because of their small size and lack of development, are considerably more vulnerable to physical damage and disease. In contrast, trees that are larger than saplings are difficult to move because of their size and extensive root structure.
When planting a sapling, its size and shape at maturity should be taken into consideration. For example, the growth of a mature tree may reach overhead power lines; alter the scale of the landscape in relationship to buildings; or drop branches, leaves, and flowers in undesirable areas. Large roots can eventually enter and damage pipes in the ground or buckle nearby sidewalks and driveways.
Another consideration when planting a tree sapling is determining what areas it will shade when it grows to maturity. Air conditioning bills can be considerably reduced by the proper placement of a shade tree. Conversely, shade from the same tree might prevent light from reaching a vegetable or flower garden.
Tree saplings are usually purchased in a container or with their root balls wrapped in burlap. The optimum time for planting saplings is during the fall while the ground is still warm, which can encourage root growth. Supplemental watering may be required for a year or two after planting, at least until the complete root system has developed.
An advantage of tree saplings is their flexibility, which typically permits them to be trained into different forms and shapes. A fruit tree sapling can be espaliered by trimming off branches and using wire to encourage the tree to grow in one plane parallel to a wall or trellis. This enables the fruit to grow larger due to the warmth reflecting off the underlying surface. Tree saplings can also be bent, causing them to grow horizontally as indicators of property boundaries or landscape borders. The flexibility of tree saplings helps them bend in storms and avoid serious damage.