Citrus fruits are shallow rooted evergreen trees. They are adapted to a wide range of climates, though they prefer warmer ones. Citrus trees grow in flushes, the main one being in spring and they are dormant in winter. During dormancy, they are relatively frost resistant. When frost damage does occur, resist the temptation to remove the damaged material until all danger of frost has passed. The burnt foliage helps to protect against further damage. Frost during the spring growth phase is the most damaging.
Citrus are nearly all self fertile and will tend to set more fruit than is needed. However, most varieties are self thinning, surplus fruit falling over a period of three months. There is also a period of pre-harvest drop when almost mature fruit will fall. This is most troublesome with Navel oranges, grapefruit and Ellendale mandarins.
The fruit matures over quite a long period and harvest can be as long as five months. The fruits are best harvested with secateurs, cutting the stem close to the button.
Citrus are heavy feeders, so plenty of good compost is needed to attain reasonable yields. They respond well to organic culture, most organic growers rating them as easy to grow. Their shallow roots necessitate mulching and nearly always irrigation is required. They are prone to a variety of trace element deficiencies and these are generally remedied with seaweed in the mulch, or foliar sprays of Seasol, or Maxicrop.
Young trees are best planted out in early spring, when any frost danger has passed. To ensure the good drainage they demand, plant on a mound. Citrus grow into large trees and are generally planted 6-7 metres apart To induce earlier fruiting, recent plantings have been at half this distance, every other tree being severely cut back when the trees begin to touch. In the home garden, the trees recover well from severely cutting back whenever they become over large. Pruning is generally confined to removing branches too close to the ground and dead wood. The bark is prone to sunburn, and painting exposed wood with white paint will prevent this.
Scale insects are the chief pest and are readily controlled with sprays of white oil. Half strength Bordeaux is used to control fungal diseases and is often mixed with white oil to improve its persistence. Do not spray in very hot or very cold conditions.
Citrus root stocks are propagated by seed.
Citrange is best when replanting into soil that has previously grown citrus. It produces a medium size tree and allows closer planting. It is susceptible to Scaly Butt virus.
Citronelle, or Rough Lemon makes a vigorous tree that is susceptible to Collar Rot. Suits lighter, well drained soils.
Sweet Orange produces high quality fruit on a more compact tree. Best on light sandy soils. It is susceptible to Collar Rot.
Trifoliata produces a small tree, resistant to Collar Rot. It is very susceptible to Scaly Butt and will not tolerate salt or a lot of lime.
Calamondins are often mistaken for Kumquats. The fruit is a little larger, but bitter and inedible raw. It makes a good marmalade. Calamondins have 9-10 segments whereas kumquats have only 4-7.
Grapefruit needs long, warm summers to produce high quality fruit. Wheeny is the best variety where these requirements cannot be met,
| Name | Comments |
| Marsh Seedless | The most common variety. Matures from early winter onwards. Creamy white flesh and mild flavour. |
| Ruby | Pink flesh. High heat requirement. |
| Thompson | Pink flesh. High heat requirement. |
| Wheeny | Green-yellow skin. Juicy, lemon like flavour. many seeds. Matures in spring and fruit hangs until early autumn. |
Kumquats are small, attractive trees and the most hardy and cold resistant of the citrus family. Flowering is late, so frost does not affect fruit set. The fruit resembles a small orange with very thin skin. Their odour is magnificent.
They are eaten raw, made into marmalade and make an excellent liqueur that rivals Grand Marnier.
Lemons are more cold tolerant than most other citrus. In frost free areas they often bear almost year round. A reduction in soil moisture will stimulate the production of a summer crop the following year. This crop is more valuable than the winter crop as the bulk of production occurs in winter.
| Name | Comments |
| Eureka | Less vigorous than Lisbon. Few thorns. Graft onto Citronelle or Sweet Orange root stock. |
| Lisbon | Vigorous. Heavy cropper. Prolific large thorns. Graft onto Trifoliata or Citrange (better) for growing in heavy soils. |
| Meyer | Small, compact tree. Sweeter than other lemons. A favourite of home gardeners. Very juicy. The least sensitive to frost. Graft onto Citronelle, or Sweet Orange root stock. |
| Villa Franca | Main commercial variety in Queensland. The fruit resembles Lisbon. Can be budded onto Citrange or Trifoliata root stock. |
Limes are acid fruit with an excellent flavour. They are very frost sensitive and only produce well where the summers are hot. The fruiting period is extended, though pre-harvest drop affects many varieties. They are mainly used for juice, though they make a good accompaniment to Tequila. You will probably only be able to purchase Tahitian Lime in Australia. This is an almost thornless variety with seedless fruit. Dried lime leaves are excellent for flavouring soups!
Mandarins need more heat than oranges and are more frost resistant. They are small trees and so are good in the home garden. Fruit set is improved by cross pollination.
| Name | Comments |
| Ellendale | Late maturing. The fruit is large and juicy, but not as easy to peel as other mandarins. The tree is larger and more frost tolerant than other varieties. |
| Emperor | Mid-season. Large tree with large juicy fruit that has a rough skin. Excellent flavour. |
| Imperial | Early. The fruit needs thinning. Dry insipid fruit. Its only virtue is its earliness. |
| Kara | Very late. Matures in spring. The fruit is large, juicy and has excellent flavour. |
| Unshui Seedless Satsuma | The earliest mandarin. Will grow in cooler conditions than other varieties. Matures late autumn to early winter. The fruit is juicy and mild. |
Oranges need a long, mild, warm growing season. They are tolerant of winter frost, but are very susceptible to fungal disease in humid coastal climates.
| Name | Comments |
| Joppa | Matures in spring. |
| Mediterranean Sweet | Matures in spring. |
| Valencia | Matures in summer. Fruit sometimes reverts back to green, but this is only a cosmetic defect. Tends to biennial bearing. The fruit hangs on the tree for a long time and may dry out. |
| Washington Navel | Matures in winter and harvest can be up to three months. The fruit loses its character towards the end of harvest. The fruit is large, juicy and seedless. |
| White Siletta | Matures in spring. |
Tangelos are a cross between mandarins and grapefruit. The fruit is the same size as an orange, which it resembles. The harvest period is only about one month. Fruit set is improved by cross pollination.
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© Jonathan Sturm 2003 - 2011