"Grafting" is the term commonly used to describe attaching a scion -- a stem, branch or bud -- of one plant variety onto the rootstock -- or bottom -- of another plant variety so the two parts join and grow as one plant. T-budding usually works best for citrus trees, according to a University of California Division of Agriculture and Natural Resources publication. Techniques called whip grafting and bark grafting work, too.
Climate and Rootstocks
Most species of citrus trees (Citrus spp.), including the widely grown sweet orange (Citrus sinensis), are hardy in U.S. Department of Agriculture plant hardiness zones 9 through 11. The mandarin orange (Citrus reticulata), however, is slightly more cold-hardy, withstanding somewhat colder weather; its USDA zones are 8b through 11.
A orange tree scion grafted onto the rootstock of a trifoliate orange tree (Poncirus trifoliata), hardy in USDA zones 6 through 9, does not share the trifoliate's USDA zones afterward, but, after several years, it becomes more cold-hardy than it would be if it hadn't been grafted.
Standard-size orange trees grow about 15 to 20 feet tall, and dwarf varieties become about 5 to 6 feet tall. Grafting a standard-size orange tree's scion onto the rootstock of a dwarf orange variety can result in a tree shorter than the standard-size tree normally would grow..
- T-budding may be the easiest grafting technique to learn.
- Whip grafting uses more scion wood than T-budding, and the grafted plant matures more rapidly than in T-budding.
- Bark grafting is used for mature trees and branches.
The scion wood used for T-budding grafting is called
A rootstock of 1-inch diameter or less is best for beginners to use for T-budding grafting.
Make a T-shaped cut roughly 8 to 12 inches from the ground in a citrus tree's rootstock by using a grafting knife. The vertical part of the T should be about 1 inch long. The horizontal top of the T should wrap about one-third of the way around the rootstock's circumference.
Loosen the flaps of bark at the top of the T in the rootstock by using the tip of the grafting knife. Take care not to cut through any buds on the bark.
Cut at a downward angle through the budwood you want to collect from a branch of the citrus tree selected as the scion. Begin cutting 1/2 inch below a bud on the branch. End the cut 3/4 inch below the bud on the opposite side of the part of the branch facing you. A budwood should be a small, thin slice that contains bark and only a bit of wood beneath it.
Cut horizontally through the top of budwood about 3/4 inch above the bud. Remove the budwood piece from the branch.
Slip the bottom, angled part of the budwood into the T-shaped cut on the rootstock. Ensure that the green, living tissue of the budwood and the rootstock contact each other. The place where the budwood and rootstock join is the graft union. Wrap the graft union with grafting tape.
Wait for the graft union to heal. The healing process takes three to four weeks in spring and six to eight weeks in fall. When the graft union has healed, remove the grafting tape and cut all leaves and shoots growing on the rootstock from 12 to 14 inches above the grafted budwood.
Cut through the rootstock about 1/8 inch above the graft union after the budwood grows a few leaves.
Whip grafting is the best technique for grafting citrus rootstocks 1/4 to 1/2 inch wide. It is done in spring or fall; if you graft in fall, give the graft union additional protection from cold. Whip grafting requires the use of grafting wax.
Make a long, sloping cut roughly 1 to 2 1/2 inches long in mature, hard green wood of the citrus tree to be used for the scion. The scion piece should be 6 to 9 inches long.
Create a long, sloping cut on the citrus tree selected as the rootstock. Ensure that cut matches the cut you made on the scion.
Make a matching vertical cut in both the scion and rootstock that will lock them into place when the scion is pushed against the rootstock.
Push the scion against the rootstock. The place where the two parts join is the graft union. Wrap the graft union with grafting tape to hold the two parts together.
Spread a thin layer of grafting wax over the graft union. The wax seals the union.
Provide shade for the graft union until it heals.
Wait for the grafted scion to grow new leaves. Prune growth from the rootstock after the grafted scion produces leaves.
Bark grafting is done early in spring when bark can be separated easily from the wood.
Saw off the trunk or a branch of the citrus tree that will function as a rootstock. Make the cut horizontally just above a branch collar -- a raised area from which a branch or smaller branch grows. Do not rip the bark.
Cut 2 1/2- to 3 1/2-inch-long vertical slits through the bark to the wood of the remaining portion of the rootstock's trunk or branch. Use a grafting knife for that task. If the slits encircle a cut trunk, then they should be 3 to 5 inches apart.
Select scion pieces that each has four to six buds. They can be up to 1 inch wide and 5 to 6 inches long. Cut a 3-inch-long sloping or angled cut at each one's bottom end.
Lift the bark on one side of a slit on the rootstock, using the grafting knife. Insert a scion piece into the slit, with the flat side of the scion's angled cut facing the green wood of the rootstock. Repeat those tasks with the remaining scion pieces.
Secure the scion pieces in place with tree tape. You can also use strong cord or thin flat-head nails.
Coat all cut areas, including the tops of the scion pieces, with grafting wax.
Paint each graft union, the areas around the graft unions, exposed trunk portions lower than the graft unions and the grafting wax with white, interior, water-based paint. Use the paint either full strength or diluted to 50-percent strength with water.
Wait for the scions to begin to grow. Determine which scion is the most vigorous grower, and remove the other scions.