A bud is an embryonic shoot that grows at the tip of a stem or at the base of a leaf. Some buds are vegetative, meaning they produce a shoot with leaves; some are reproductive, meaning they produce flowers; and some yield both leaves and flowers. Some buds form at the end of a growing season and lie dormant until the next spring; these buds are said to be resting. Buds that wait for years before they begin to grow are called dormant.
Many buds are protected by external scales that come in different arrangements, colors, number, shapes and sizes. Some are covered with short hairs, called pubescence. Those buds that have neither scales nor hairs are called naked buds.
Terminal buds are the fat buds that grow at the tip of a shoot or branch. Terminal buds produce auxins, growth hormones that make them grow faster while the other buds remain dormant. This dominance is said to be apical, meaning "at the tip." Removing a terminal bud will cause the bud immediately behind it to break dormancy. The terminal buds dominate those buds below them. Special tissue called apical meristem in terminal buds can divide indefinitely.
Gravity pushes auxins down branches. Auxins do not move up branches, so buds that produce flowers on vertical branches receive less auxin. Buds on branches growing at a 45- to 60-degree angle from the trunk yield the most fruit.
There are three types of lateral buds that grow along the length of a branch. Buds that produce side branches are oblong and rounded. Buds that produce leaves are triangular and flat; they may grow as axillary buds at a leaf petiole---the point where the stem of a leaf meets a twig. Round, plump buds that produce flowers may also grow at the base of leaves. If buds that produce leaves or flowers do not receive sufficient sunlight, they will wither.
The leaves of developing buds that produce flowers must receive at least 30 percent of full sunlight to supply the carbohydrates needed for the bud to produce flowers the next season.
Buds that persist on older wood are connected to the plant's vascular system and are small and under-developed. If a branch is cut or broken off, a latent bud will yield a new shoot---the plant's way of restoring itself if it is injured.
When a plant is injured or its mature branches are proned, an adventitious bud may grow to continue the growth of the plant. Adventitious buds produce weak branches, because they lack a good connection to the vascular system of the plant.