3,573. Grafting Young Trees to Old Trees
Hilchos Maaser Sheini and Neta Revai 10:15
If the new growth from the extension grew fruit and was later separated from its source – the original tree – orlah is counted from the time of its separation. Nevertheless, the fruit that grew before separation remains permitted because it grew permitted. If the fruit was left on after the new growth was separated from the original tree until it increased 1/200 in size, then it is prohibited.
Hilchos Maaser Sheini and Neta Revai 10:16
If a young tree is grafted to an old tree and there was fruit on the young tree, all that fruit remains prohibited even if it increases 200 times in size. This is because permitted fruit can’t permit something inherently prohibited.