Citrus volkameriana is a citrus producing round lemon-like fruits which for all intents to us should be treated as rather tasty lemons. Technically Citrus volkameriana is a hybrid, some say a cross with a lemon and orange others a lemon and a citron. I’m not sure but what I can tell you is that Citrus volkameriana is fast growing, free flowering and fruiting and generally easy to grow compared to a ‘normal’ lemon. Hardiness too is improved with plants capable of withstanding frosts down to -5 degrees C.
Worth a try outside in the UK? Maybe if you have a very sheltered garden and perhaps a south or west facing wall. For most of us I’d suggest growing outdoors in a container protecting during the worst of winter in a cool conservatory or glasshouse.
Use ericaceous compost and regular feeds of dilute seaweed feed or citrus fertilizer. Citrus volkameriana can easily be pruned to shape too.