Your guide to growing citrus

What is an Aussie garden without a lemon tree? In some cases, it’s the only plant in a neglected backyard, uncared-for and forlorn but battling on year after year. Citrus is the number one fruit tree type grown in Australian home gardens and for all but the coldest parts of the country there are excellent varieties that are suitable for home use. It often comes as a surprise, though, that citrus plants are native to South East Asia rather than southern Europe or the Middle East.

You can understand the mistake, as citrus has become a commercial plant much associated with the Mediterranean and the Middle East. Here, we look at some of the popular and unusual varieties of citrus available to home gardeners and offer some recipes that will encourage you to plant some citrus.

Lemon

For many Australians, the most popular citrus used in cooking is the lemon (Citrus limon). From a simple dressing for fish and chips to Greek tzatziki dips, the lemon has been the acid juice of choice since early settlement. Oddly, most Asian recipes when they call for lemon as an ingredient — and many do — really mean lime; visitors to South East Asia will find that lemons are rare as they dislike tropical climes. Lemons have an obscure genetic history and may have been bred through crossing several citrus parents in Europe or the Middle East.

Perhaps due to its culinary popularity as well as ease of culture, the lemon is arguably found in more Australian gardens than any other fruit tree. They grow well in most of Australia, apart from the true tropics or areas with hard winter frost. The two main varieties of lemon available in Australia are Eureka and Lisbon.

Eureka is the most common lemon grown in home gardens as it’s a prolific fruiter and bears few thorns. Its main downside is it dislikes frost. One of the oldest varieties of lemon in Australia is Lisbon, which is more cold-tolerant than Eureka, but has the disadvantage of being a much thornier and less prolific plant.

Oranges

The main commercial citrus crop in Australia is the sweet orange (Citrus sinensis), the main varieties being the Washington Navel and the later fruiting Valencia. It’s said that if you plant one of each of these varieties, you’ll have oranges available at home for 10 months a year. Oranges are easy to grow and, like most citrus, demand regular water and fertiliser and free-draining soil.

For those wanting to use oranges in jams and cooking, a sour orange or Seville (Citrus aurantium) is worth choosing, especially as they are hard to find in fruit shops. Sour oranges arrived in Europe from China in the 1st century BCE and were well established in southern Europe by the 4th century CE. Seville oranges remain popular in warmer parts of Europe and are essential for making orange marmalade.

Mandarin

Mandarins (Citrus reticulate) are the most popular eating citrus and are gorged in vast quantities by children and adults during winter. The biggest-selling variety locally is the early-fruiting Imperial, which is at its best in early winter. This locally raised, easy-to-peel variety dominates the Australian mandarin market despite having less flavour than many later varieties.

Mixed parentage

Many commonly available citrus plants are in reality artificial crosses between two or more parents. One popular cross is the Tahitian lime (Citrus latifolia). This lime is the most common lime grown in Australian gardens and it comes as a shock to some that the plant is not a true lime, even though it looks and tastes like one. The Tahitian lime seems to be a cross between the West Indian lime (Citrus aurantifolia) and the citron (Citrus medica). This inspired cross allows limes to be grown in temperate climates and the plant can even take minor frost.

Another popular cross is the Meyer lemon (Citrus x meyeri). Rather than being a true lemon, it seems to be an early Chinese cross between an unknown orange and a lemon. Sweeter and less sour than lemons, it makes a good choice for regions with frost, climates usually unsuitable for true lemons. Meyer makes a fine pot specimen, too.

Collectors Corner

One of the most popular citrus in recent years is the limau purut (Citrus hystrix), a plant better known by the offensive name kaffir lime or the more acceptable Thai name, Makrut lime. This highly aromatic plant is grown for its unusual double-jointed leaves and knobbly green fruits, which are used in Thai dishes.

Lovers of native plants will be happy to discover there are some citrus species that come from Australia. The most promising candidate is the Australian finger lime (Citrus australasica). An unusual citrus, this plant is a spiny species that produces long, narrow, sour fruits that can be used in cooking and preserves. A variety known as Rainforest Pearl is preferred.

Ornamental and pot varieties

Despite Australia being ideal citrus-growing country, the ornamental possibilities of citrus have been virtually ignored by local designers. The Chinese have cultivated citrus for 3000 years and rarely plant them in the ground, preferring pot-bound specimens. Citrus grow very well in pots as long as water is given to them regularly during warm weather.

As well as pot specimens, citrus can also be formally planted in rows, a style much associated with Moorish gardens found in North Africa and Southern Spain. Pot-bound specimens are often affected by leaf mining insects, which tunnel within leaves. While rarely detrimental to the overall health of the plant, these insects can be controlled by regular sprays with Pest Oil® during spring, summer and early autumn.

Varieties for hot and cold climates

Citrus plants can be grown almost anywhere in Australia as long as water is available. While most dislike frost, there are several varieties that tolerate the cold. The best citrus for frosty areas are the mandarins, cumquats and some oranges. The most cold-tolerant mandarin is the Satsuma. This is an early-ripening, seedless variety originating from Japan and will survive up to -10°C. While the satsuma is the cool-climate toughie, cumquats and oranges, especially Washington Navel are also frost-tolerant. For cold climates, make sure to select citrus grown grafted onto trifoliata rootstock (Poncirus trifoliata); this hardy root system gives the trunk of the tree some defence against cold.

The other extreme for citrus is the tropics, but even here there are citrus that grow well, not surprisingly as citrus comes from Asia. The best citrus for the tropical north of Australia is the West Indian lime and the pomelo. West Indian limes (also known as key lime or Mexican lime) are the limes grown in the tropics and should not be confused with the Tahitian lime, which grows best in temperate areas. The tropical lime is equivalent to the temperate lemon and adds acidity and taste to Asian dishes.

The pomelo, or shaddock (Citrus maxima), is the largest member of the citrus tribe and looks like a massive grapefruit. Popular in Asia, these beautiful sweet fruits are rarely grown locally, although they are easy to grow. The tree grows to 8 m, and it is said that the blossom is one of the most outstanding fragrances within the family.

Pests and diseases

Perhaps due to its popularity with home gardeners, citrus is the most asked-about plant in garden phone-in sessions on local radio. These queries relate more to the fruit’s popularity than to any reputation for being problem-prone. Typical queries relate to lack of fruit, pests and diseases and correct times to fertilise.

Fertilising confuses many home gardeners. Citrus require plenty of high-nitrogen fertiliser, ideally in early spring and around mid-summer. Make sure the mix is applied to wet soil and water in after application. I like to mulch my trees with hay or straw mixed with some chicken manure. Make sure you keep the collar of the plant away from the mulch to avoid collar rot.

Citrus demand full sun to flower and fruit well. The only exception is for pots in the middle of summer when light shade protects the plant against heat and water stress. Major citrus pests are scales, beetles and bugs. These can be treated by various means, but require proper identification before attempting a cure. A great reference is Judy McMaugh’s, What Garden Pest or Disease is That?, or try looking at websites managed by state agricultural departments.

But, despite their many pests, citrus are easy ornamental plants to grow and make a satisfying low-maintenance fruit tree for the home garden.

Silas Clifford-Smith is a New South Wales horticulturist with an interest in growing fruit trees.

For more information on growing citrus such as pruning lemon trees as well as gardening and backyard design advice visit Complete Home,