the.com/rootstock
the plant does the growing, but the roots decide the rules.
means the root and lower stem of one plant onto which a different plant's shoot is grafted, so the roots' hardiness drives the visible plant's growth.
from from grafting practice going back over 2,000 years, formalized by 19th-century viticulture after phylloxera nearly wiped out europe's wine grapes.
phylloxera fixamerican rootstocks saved european vineyards in the 1800s
dwarfing trickapple rootstocks control tree size, not the fruit variety
same fruitcloned scion means identical fruit regardless of rootstock genetics