Common name: Mistletoe
Remember that mistletoe is a parasite and its growth may affect the growth of the branch it is on,which in the case of an apple tree may affect the fruit yield.
Mistletoe grows very slowly so it'll be some time before you get a significant plant, up to four years in some cases, so patience is the order of the day.
But once established it grows quite fast.
Mistletoe is diocieous meaning that both male and female plants are required to produce berries.
All parts of the plant are poisonous though the toxicity level is very slight.
Harvest fresh berries circa Weeks 4-10, failing that buy them from a specialist supplier.
Berries saved from sprigs used during christmas festivities are less than ideal and are unlikely to germinate.
Week 4-10: Crush five or six mistletoe berries and press both the seed and the flesh into fissures on healthy bark of your host tree, the pulp will eventually harden, and the seed will hopefully root.
Choose young branches, from 25-50mm (1"-2") diameter, avoid older branches and the trunk.
There is no need to cut flaps in the bark to perform this task, the indentations in the bark surface will suffice.
The success rate can be low so it is advisable to sow numerous seeds on various branches to increase the chances of success.
Mark/tag the branches used in order to remember the sowing location when monitoring progress.