Eucalyptus citriodora is a tall water hungry tree to 50m in warm climates but can be kept pollarded if grown in a pot for the UK. It is not frost hardy and not suitable for growing outside all year round in mainland England. The lemon scented leaves are used to produce an essential oil used as an antiseptic or insect repellent. A herbal tea can be made using an infusion of the leaves for treatment of fever. I have seen it mentioned to use as a herb on food but Eucalyptus oils can be mutagenic and it would not be my advice to use it this way. On the plus side and quick from seed it will make an excellent highly lemon scented patio pot plant for the summer with long lance shaped bright green leaves.