The sweet smell of its blossoms, glossy dark-green foliage, and brightly coloured fruit combine to make citrus one of the most ornamental and useful plants you can have in your garden. Just about every type of citrus is outstanding in this regard, with both fruits and foliage being useful in the kitchen. The abundance of aromatic oils in most parts of the plant means that even the fruit rinds can add that special touch to recipes.
An interesting thing about citrus fruits is the way they have evolved in cultivation in much the same way as domesticated animals, such as horses and dogs. Even though the original wild species of citrus come from Southeast Asia, some of the most popular cultivated types have exotic names, such as the Palestine sweet lime, Tahiti and West Indian limes, and the Lisbon lemon. These names reflect the fact that these varieties have arisen in cultivation after the various types of citrus were distributed to far-flung corners of the globe in the course of human history. The geographical range of these exotic-variety names is also a testament to just how adaptable this group is to an array of climatic conditions. Their only major weakness is a susceptibility to heavy frost.
Although some of the citrus group, such as oranges, lemons, and grapefruit, can grow into substantial trees, others, such as mandarins, cumquats, and limes, are much smaller; making it possible to grow these types in large pots. This is by no means a new concept: In Europe in the 17th and 18th centuries, elaborately constructed greenhouses known as orangeries and limonaias were heated to overwinter the frost-tender citrus family. Louis XIV created the most famous of all orangeries at Versailles, where the lemon trees were grown in solid silver tubs, an idea that would certainly make a statement in your courtyard garden. Fortunately, in most parts of Australia and New Zealand, thereâ€™s no need to lug big citrus pots around in winter â€“Â they can tolerate the light frosts that most gardeners experience. If you live in a very cold climate, grow them in a protected spot, such as within a courtyard or beside a wall.
Try these on for size
When growing citrus for small spaces, possibly the best are the Nagami, or oval, cumquat (Fortunella margarita) or the Marumi, or round, cumquat (Fortunella japonica). You can consume the tiny fruits of these attractive plants whole or use them in various culinary pursuits. Both species grow to only a couple of metres; therefore, itâ€™s easy to grow them in even a moderately sized container of, say, 25-30cm diameter. Cumquats also lend themselves to the formal look of a standard (i.e. a plant that is shaped into a ball or is allowed to spread out at the top of an elongated stem), which you create by allowing the leader stem to reach a height of 1.5 to 2 metres, then pinching the growing tips every few weeks during growing season to make a spherical shape.
The lime (Citrus aurantifolia) comes in a number of varieties, all growing to approximately 4 to 5 metres. Tahiti, or Persian, limes boast relatively large fruit, whereas Mexican, West Indian, and Colombian sweet limes have smaller fruit with stronger flavour. The attractive-lobed, shiny leaves of the Kaffir lime are highly prized as an essential flavouring for Thai and other Asian cuisines. Itâ€™s also one of the best to grow in a pot, and its glossy green leaves look particularly attractive â€“ almost too good to eat!
The mandarin (Citrus reticulata) is another of the more compact citrus species, growing to a manageable 3 to 4 metres. Although Imperial is perhaps the hardiest of the mandarins, Ellendale has tasty, sweet fruit, and Clementine has proved to be a better performer in cooler climates.
Another option for growing citrus in small spaces has come about through the introduction of a special rootstock, Flying Dragon, which limits the size of citrus varieties that are grafted onto it to a far more manageable size for small gardens, courtyards, and balconies. This extremely useful rootstock dwarfs all types of citrus, so even the taller growing types, such as lemons and oranges, can now fit in a courtyard garden. The fruits are still the same size, but the plantâ€™s height and width are reduced.
Fragrant and flowery
The tantalising taste of the various citrus varieties is reason alone to grow them. However, these fruits also tempt another of our senses with the heady perfume of their white starry flowers. Most types flower in spring, then develop fruit through summer. This is a crucial time to keep them evenly watered through regular irrigation (say, one deep watering a week) and a 10cm layer of mulch, such as Lucerne hay. Itâ€™s important to keep the mulch away from direct contact with the trunk to prevent fungal problems such as collar rot.
Citrus fruits of all types benefit from a light trim in late winter to keep them compact and bushy. You can prune back stems up to the thickness of your index finger, but I donâ€™t recommend this unless the tree is really in need of reshaping.
The most common pest problem is leaf-miner during the warmer weather, so be on the lookout for leaves with a scribble pattern on the surface. It occurs mostly on fresh new growth. You can pinch off affected leaves to prevent the problem from spreading. Scale insects and aphids feeding on the leaves and stems are other common issues with just about every type of citrus; often, black, sooty mould growing all over the plant indicates their presence. By eliminating the sucking insects, you can stop the sooty mould. Using horticultural oils, such as pest oil, is a very low toxicity way of controlling these pests. Spray as directed onto the stems and both surfaces of the leaves during the cooler parts of the day.
Feeding your fruit
For citrus in large containers, use a potting mix designed for this purpose, such as a terracotta-and-tub mix, which not only holds plenty of water, but also gives the roots the good drainage they need to thrive. As far as fertiliser goes, the diluted liquid from a worm farm or a few good handfuls of well-rotted cow or horse manure can keep your citrus glossy and dark green. If you donâ€™t have access to these organic options, itâ€™s a good move to sprinkle controlled (slow) release fertiliser evenly on top of the mix once in early spring and again in late summer to keep the plants growing well. You can also fork water-storing granules into the mix if the plants are drying out excessively in the summer months.
If you can keep up the watering of your citrus through the hot summer months, youâ€™ll be richly rewarded with juicy, tree-ripened fruit that will make a world of difference to your fruit consumption and culinary pursuits.