Grafting an orange tree is called budding. It is the correct way to propagate citrus trees. Citrus trees require grafting onto an appropriate rootstock to do well. Budding ensures that the new tree will be true to the cultivar, as seeding is not a guaranteed process.The rootstock used should be less susceptible to disease or rot and grafted trees mature sooner and produce better than seeded varieties.
Oranges are not wild trees. They are a created cultivar from other citrus. Oranges most probably originated in China or perhaps India and were brought to the U.S. by Spaniards. The trees can be 25 to 50 feet tall and dwarf varieties exist that are suitable for containers. It is a tropical to sub-tropical tree that is sensitive to extreme cold and freeze. Grafting onto rootstock can decrease the susceptibility to extreme temperatures. It can also minimize disease and fungal issues that occur on the original rootstock. The Europeans practiced budding in the 16th and 17th centuries and the process was probably a result of watching seedlings graft to each other in nature.
The originally used rootstocks were sweet and sour oranges and rough lemon. Sweet orange was found to have a problem with foot rot, so it is no longer used. Sour orange was then used but the trees were small and did not produce well. Rough lemon grew vigorously and quickly and was found to be more resistant to cold and foot rot. It became the predominantly used rootstock in Florida until growers realized it had problems with blight. Rootstock used today varies depending on country and conditions, but sour orange and rough lemon account for approximately 75 percent of rootstock worldwide
Budwood comes from the original tree (scion) that needs to be propagated. It is best to harvest in April through November when the wood is soft and easy to separate from the tree. Grafting is best described as "wounding and healing;" a process necessary to have the budwood adhere to the graft. Collecting second season young round budded twigs and then trimming them to eight inches is the first step. These pieces need to be used within three months and stored in a plastic bag in refrigeration.
The rootstock needs to be healthy. A very sharp knife is needed to cut an upside down T shape in the stem. A piece of budwood is sliced with the bud intact, in a narrow sliver of wood. The wood sliver is pressed into the T. The bud should be enclosed by the wood in the rootstock. The graft needs to be wrapped with bud tape both above the budwood and below it. The tape stays on for 30 days and when removed healthy green should show, indicating the graft took.
Any citrus can be grafted to a rootstock. The most important considerations are the health of the scion and the bud stock must be "slipping" or easy to separate from the tree. A sharp clean knife is important. It must be clean to prevent introducing disease into either the scion or the rootstock. Additionally the graft needs to be kept moist but not wet. Periodic misting is adequate. Budding has helped create a booming orange industry, with delicious fruits that are hardy in a variety of situations.