I purchased a concord grape at a big box store about five years ago. I watered it in the first year (by hand). I literally forgot about it. It struggled for three years. Starting last year it became more vibrant. I'm not sure if It helped but I planted a comfrey plant right on it, and chop and drop regularly. I really should have done a better job of trellising.
After the first year I didn't do anything for three years. Last year I started to keep grass clear at the base. This is the fifth year and it is loaded with fruit. The only water it gets is natural rainwater that falls from the sky. Outside the fence is grass and wildflowers, that have gone feral, and the inside is heavily chipped.
Wine grapes usually have rootstock. Phylloxera wiped out almost all of France's wine grapes so a lot of the vineyards there are using u.s. rootstock.
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