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Well the more sunlight then the sweeter the fruit no?
Khajiit is unsure if there is significant body of lore on the art of fruit cultivation in Tamriel but from observation the Gold Coast is well known for the fine grapes.
A climate offering both warmth, rich soil and enough water would probably be best.
Khajiit has tried growing them at Castle Claws and at Claws Temple Spa resort. Both have a similar climate.
At Castle Claws though the carrot tree does much better than the grapes. The vineyard at the temple has not yet has chance really to yet become fully established.
In Oblivion, the region around Skingrad is called "the wine-producing capital of Tamriel", and that "Skingrad's wines are the best in Tamriel". (Although that are quotes from the local vintners, so maybe not completely objective. ) In that game, Surilie is a specific family-owned vineyard and winery; the relation to ESO's Surilie grapes and wine not being entirely clear.
In ESO, that would be the region around Vlastarus.
@Bansidhe1965: @Bruccius and @Varana have your answers for the official lore on what is known of Tamrielic grapes and wine. Let's also not forget the Surilie Brothers' biggest competitor, Tamika, right across the road!