Varies with type. Kind grown for years in Washington Park Arboretum, Seattle (USDA 8) did have some browning in 1990 winter (coldest in 30 years).

Wild species are not clones, unlike many cultivars, unless it happens all the stock in cultivation is from clonal propagation of single selection. This is far from the case with tea.

thank you BBoy.
Well, I put myself in zone 7, but in this corner of northern Italy the temperature rarely drops below 14°F, and only during a few hours in the morning, otherwise we are above freezing point. (apart from 1985 when we were at -4°F almost for the whole january, due to snow and fog, but quite exceptional)

That month(!) of -4F must have been highly destructive. Rarely below 14F sounds like USDA 9, there was probably alot of tender stuff lost there that year.

Here is a link that might be useful: italian gardening zones

Yes, even fig trees died to the ground, but they sprouted again in spring.