Grafting is the process of merging a young, fruit-bearing limb to an older, established fruit tree for the purposes of reinvigorating the older tree. Plants that are in the same family but of a different variety can be successfully grafted. With regard to citrus, any type of citrus fruit can be added onto any other tree, such as an orange to a lemon tree. The young tree should be disease free, and grafting will be more successful if both trees are healthy.
Select the budwood from the desired variety of orange tree and remove it from the branches. The best budwood is new growth with multiple leaf buds, as well as its accompanying bark. The tree that the growth is taken from should be disease free to avoid infecting the lemon tree.
Saw off a limb from the lemon tree, leaving behind 1 foot of the branch.
Cut a 2-inch cleft into the center of the lemon tree's limb using a cleft knife.
Cut the orange budwood with a grafting knife so that it forms a V-shaped point at the bottom. The cut should be no longer than 1 1/2 inches.
Press the orange budwood into the lemon limb until the green middle pieces match up.
Cover the entire graft in grafting compound.
Watch for signs of growth on the lemon tree. If the orange tree's buds are growing but have not formed leaves within 8 weeks, remove any lower branches from the lemon tree to encourage more nutrient dispersal to the orange branch.