I've tried growing Myrtle in a cooler climate, and it can be a bit challenging but definitely possible with some effort. Overwintering is crucial; I usually keep mine in a pot so I can bring it indoors during particularly cold spells. A position near a bright window works well. In terms of maintenance, regular pruning helps keep it tidy and encourages bushier growth. Do watch for water needs – it doesn't like being too dry, especially in a pot. Have you thought about using a frost blanket or mulching heavily if you're keeping it outdoors? That might offer some extra protection.
