What is the question "Mah Yihyeh Etz ha'Gefen mi'Kol Etz"?
Rashi: What is the end of a vine ? [how is it different] from all other trees?
Radak: How is the vine inferior to all trees?
Malbim: Planters often graft or are Mavrich 1 branches of fruit trees on other fruit branches. Via the grafting, the branch nurtures from the stump of the other species, and produces fruits that are a blend of the source species. E.g. if one is Mavrich vines onto a fig tree, the sweetness of figs will be drawn into the vine. 'One may not insert a vine into a melon, so that the melon will shoot its juice into it' (Kil'ayim 1:8). They also graft weak barren trees onto strong barren trees, to thicken them. However, one who grafts a vine onto a barren tree does not gain at all. This ruins the fruit, and the vine does not become thick and strong via the graft. The verse asks, what will come from grafting a vine onto another tree?
Havrachah is inserting the end of a branch vine in the ground (Rashi Rosh Hashanah 9b), so it will take root and come out elsewhere. Kil'ayim 7:1 calls [also] inserting it into a Pri 'Havrachah'. (PF)
What do we learn from "ha'Zemorah Asher Hayah ba'Atzei ha'Ya'ar"?
Rashi: I do not ask about a vineyard vine that bears fruit. Rather, I asked about a vine that grows in the forest.
Radak: I do not ask about a vine that bears fruit ? it is esteemed! Rather, it is a forest vine, It is like forest branches, which do not make fruits. The latter are useful, to make Kelim from them or make a house roof; vines are not proper for this.
Malbim: This explains that we discuss grafting a vine onto a [barren] forest tree. Grafting a weak barren tree onto a strong barren tree, it thickens and strengthens ? but what will come from a vine? Its substance is very weak!
