Use a sharpened knife to take the scion wood from the baby orange. Wipe the knife with alcohol to sterilize it and prevent the spread of disease to the new plant.
Remove from a mature tree — in early summer — a healthy, swollen bud that has not yet opened. Use a scooping or slightly C-shaped cut to remove the bud and a small amount of wood on either size. Cut behind the bud so it is intact after you remove the wood. The total piece of wood should be less than 1 inch long.
Cut an upside down T in the bark of the young orange seedling that will function as the rootstock. Use the tip of the knife to gently fillet out the bark edges in the cut. This will expose the cambium which will house the new bud.
Push the bud up into the T cut and then cut off any extra wood that sticks out. Press the bark back around the bud to hold it in place.
Wrap the union with grafting tape to completely seal it and prevent insects or disease from entering. Remove the tie in two or three weeks. If the bud is green the graft worked. If it is not, try again lower down on the orange seedling stem.