"and produce of the vineyard": When is the produce rejected? When it takes root. And grapes? When they become like the 'white (egyptian) bean'.
This (verse) tells me (that it is forbidden) only in a fruitful vineyard. Whence do I derive (the same for) one that is not fruitful? From "the vineyard" — in any event. This tells me only of your vineyard. Whence do I derive (the same for) the vineyard of others? According to R. Yossi, from "the vineyard" — in any event.
If one trains a grapevine onto seeds, even for (a distance of) one one square ell, the grapevine is forbidden.