Orlah, Chapter 1, Mishnah 5. This mishnah deals with two procedures performed on trees and on vines: 'havrachah' (layering) and 'harkavah' (grafting). Their names are similar, since both are built from the same letters in a different order, and we must first clarify the difference between them.
Two concepts - havrachah and harkavah:
Havrachah (layering) - the word derives from 'berech', the knee, which bends and stoops. One would take a flexible branch of a tree, bend it downward and plant it in the ground while it was still attached to the tree, and it would come up in another place as a second tree. This procedure was especially easy to carry out with a vine.
Harkavah (grafting) - grafting a branch of one tree onto another tree, and sometimes even while it is still attached to the original tree.
A tree that was uprooted and has a layered branch:
A fruit tree that was uprooted - as we mentioned, once it is uprooted and replanted, the count of the years of orlah begins anew. But the mishnah adds: "u'vo breichah v'hu chai mimenah" - if the tree has a layered branch, meaning a branch that was planted in the ground, and the tree draws its vitality from it and is able to survive by means of it, then "chazar hazaken lihyos ki'vreichah" - the old, original tree takes on the status of the layered branch, and the layered branch is regarded as though it had been planted only now, since until this point it was living off the original tree, and therefore the clock starts over.
Layering year after year:
The mishnah continues: "shanah achar shanah v'nifsekah - moneh mishaah shenifsekah" - if each year he layered a branch into the ground, and that branch came up at some distance as a second tree, and from the second tree he grew branches of its own and layered those as well, and so on year after year, and in the end the original branch was severed from the tree, he counts three years of orlah from the time it was severed, and for all the branches that came afterward the clock starts anew.
Grafting vines:
From here the mishnah moves to the law of grafting, in which a branch is taken and grafted into another tree. With vines, one would take one of the shoots of a vine and graft it into another vine, and this is called 'sipuk hagefen'. The mishnah rules that if there was "sipuk al gav sipuk" - that he grafted a shoot into a shoot, and that one into a further shoot, and so on - then "af al pi shehibrichan ba'aretz - mutar" - that is, even if he took these shoots and performed layering with them, burying them in the ground so that they now receive their vitality from the earth, we do not say that from now on they are newly planted; rather, everything is permitted, since they are all connected to the original vine whose years of orlah have already passed.
The view of Rabbi Meir:
Rabbi Meir holds that the matter depends on the strength of the nourishment it draws: "makom shekochah yafeh" - when the ability of the secondary planting to draw from the original planting is strong - it is permitted. "makom shekochah ra" - when it does not draw well - it is forbidden, and we do not view the new planting as a branch of the original tree; rather, its clock begins from the time it was planted.
The Yerushalmi gives an interesting sign for distinguishing between the two: if the branch draws properly from the original tree, the leaves of the secondary branch turn to the side, almost like one who receives from another and is embarrassed by it and turns his face in the other direction. From this one can know that it is drawing properly.
A layered branch that was severed while full of fruit:
The mishnah continues: "v'chen breichah shenifsekah v'hi mele'ah peiros" - if one of these branches or vines was layered into the ground, and afterward it was severed from the original tree, then at the outset there was no problem of orlah with it, since the original tree had already passed its years of orlah; but once it was severed, as we learned, the clock starts anew. And here the case is that it had a great deal of fruit on it that had grown permissibly.
Therefore the mishnah draws a distinction: "im hosif b'masayim - asur" - all the growth added after the severing is considered orlah, since from that moment the clock started anew; however, orlah is nullified in two hundred and one. Therefore, as long as the added growth does not reach the measure of one in two hundred and one, it is nullified and absorbed into the original fruit, and the permitted fruit nullifies and neutralizes the new portion which is orlah. But if it added more than one in two hundred and one, there is no nullification, and the fruit is forbidden.
In summary: in this mishnah we learned the laws of 'havrachah' and 'harkavah': a tree that was uprooted and lives off its layered branch - the old tree takes on the status of the layered branch, and we count for it anew; layering year after year and then the branch was severed - he counts from the time it was severed; grafting vines and grafting upon grafting are permitted even if he layered them into the ground, as long as they draw from the original vine, and according to Rabbi Meir the matter depends on the strength of the nourishment, with the sign for this given in the Yerushalmi; and finally, a layered branch that was severed while full of fruit, where the added growth is forbidden only if it added more than one in two hundred and one, and with less than that it is nullified in the permitted fruit.