Hi Simon, I have a grapevine growing outdoors over an arch in a South facing garden & it grows like wildfire & constantly needs trimming back during the summer. I think it depends on the variety how well they do outdoors & you do need a fair amount of sun to ripen the fruit, I think mine is possibly 'Brandt' or similar & is an outdoor variety. You should have enough light & as for the roots you could always keep it in a container sunk into the ground to contain it a little.Only pruning in early spring when the sap is rising as the leaves are just starting to break can lead to a lot of bleeding, you're fine doing it in summer. Remember you might need to protect the fruits from the birds , I usually lose loads to the local blackbird!

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