Doesn't like temperatures below -5 deg C, and prefers nothing under 4 deg. C, but this is a large shrub when planted outside - if you have a sheltered, sunny spot and can provide a bit of protection (such as fleece, etc) in colder winters, then you could grow it in the ground, though you'd need to wait till late March/April to plant it out, when the weather's warmed up. Otherwise, pot up in the spring in John Innes No. 2 compost in a largish pot and stand outside for the summer, keeping it well watered, and feeding fortnightly (something like general purpose Miracle Gro will do) and move inside when winter starts again.