It is worth buying an immature vine as this will be grafted onto root stock which prevents attack by the phylloxera aphid which destroyed so much of the French grapes vines in the past. Although if you are in the UK this shouldn’t be a problem. A new vine will produce grapes after two years or more.
Grapes will only ripen if they get enough sun. A cold winter does them no harm at all. Where I live in Bulgaria there is 3 feet of snow for a couple of months a year and my vines produce heavy crops year in year out. I not only have a dessert grape vine but also several varieties of wine grapes. Which I turn into wine
How to Grow Grapes
1. You can either buy a 1 year old vine or get a cutting from an established vine and plant where it will get maximum sunshine and have a framework to climb over.
2. Pruning is essential, as the fruit only grows on new shoots, you should therefore cut back severely every year to ensure a good crop.
3. Pick when they are fully ripe and eat (if dessert grapes) or ferment if wine grapes.