The lemon tree is an ideal fruit-bearing specimen for Sydney gardens, as it thrives in our mild climate. There are several main types. 'Eureka' is the most commonly grown cultivar and it has fruit and flowers almost all year round, though the heaviest crop is in winter. It can grow about 4-6m tall. 'Meyer' is smaller, with more compact, sweeter fruit, and is very suitable for pots. Another cultivar is 'Lisbon', used by commercial growers and suitable for hot areas, but it does have thorns.
All citrus trees have particular requirements to do well. A key point seems to be to find the ideal spot in your garden for them - in a well-drained position in full sun. As with any planting, the soil should be prepared in advance, by digging over a reasonably sized area to at least a spade's depth, adding gypsum if there is a lot of clay and incorporating rotted organic matter. The roots of the plant should be teased out gently and the plant placed in a hole at least twice the width of the root ball. The plant should be put in at the same depth it was in the container, with top of the rootball should be level with the surrounding soil. Water well and keep it well watered for the next few weeks. Once established, citrus trees need regular watering and love to be fed every few months, using something like Organic Life or Dynamic Lifter. They also need to be free of competition from grass growing around their surface roots, so a good-sized area should be left clear under the tree, which can then be kept covered with an organic mulch to conserve water and protect the roots from heat. The mulch can be scraped aside whenever you are going to apply fertiliser. Don't ever allow the mulch near the trunk, as this can cause fungal problems.
Young plants should not be allowed to fruit for the first two years, as apparently this will severely affect their growth during that time. To produce larger fruit on established trees, it is a good idea to remove some of the young fruit when it is very small, or even take off some of the flowers. Although pruning is not essential (except to remove dead wood), they don't object to pruning and this is one way to reduce the number of fruit on the tree. Pruning can also be used to produce formal effects such as standards or espaliers out of your citrus trees.
Citrus trees, especially the smaller types, such as 'Dwarf Myer', can be grown successfully in pots, repotting as they grow until they finally are placed in a decent-sized container. As with citrus planted in the ground, they need regular fertilising and watering. Don't have a saucer under the pot that can collect water, as this may cause root-rot. There are various pests which attack citrus - not all affect the fruit, but they can distort the foliage. Eco Oil can be applied on a regular basis to control most of the pests, which include citrus leaf miner (prevalent in summer and autumn), the horrid bronze orange bug (which can affect the fruit as well as the foliage), scale and aphids. There are also sticky traps available to hang in the tree to attract the male citrus leaf miner in order to reduce overall population numbers; this pest is particularly active from December through to April. When establishing a new tree, it is important to control citrus leaf miners, as they will severely affect its growth.