Lime

Grafted limes begin fruiting around their third year and are self-fertile, so a single plant will crop. They are the most cold-sensitive of the common citrus and really need winter protection in anything less than a subtropical climate — a warm conservatory, heated greenhouse, or bringing pots indoors is essential. Kaffir lime (Citrus hystrix) is grown more for its leaves than fruit and is worth having alongside. Feed well during the growing season and watch for scale insects, which love citrus.