http://www.telegraph.co.uk/gardening/9173608/Zest-for-life-grow-your-own-citrus-fruit.html

Zest for life: grow your own citrus fruit
Citrus trees are a joy to grow and there’s a variety to suit every type of gardener.



Still life: a basket of zingy citrus fruit is hard to beat

By Sarah Raven
2:08PM BST 29 Mar 2012

When I was a girl, we used to rent a house in the walls of Asolo, a medieval town in the foothills of the Dolomites. There was a simple metal-and-glass structure on the side of the house, built to protect the lemon trees in the frosty months. The lemons were planted in huge and handsome clay pots, which were placed along the front wall of the house throughout the summer and autumn. When we stayed — usually over Easter — the trees were still inside their cocoon, and on opening the door to the primitive greenhouse, you were knocked back by the scent of the citrus blossom. It’s a smell I’ve never forgotten, and anything delicious I’ve encountered since has been ranked in relation to that whoosh of perfume.

For any of us who have a greenhouse, conservatory or decent-sized sunny room or porch, citrus trees have to be at the top of our growing list. They make exotic-looking large-scale pot plants, and are either flowering or fruiting in almost every month of the year. Once you’ve smelt their blossom, it’s hard not to be hooked. Every fruit looks a little different, and piled in a bowl, with a few leaves left on the stems, they make a lovely and very long-lived still life.

This all-year-round aspect is particularly true of the Four Seasons lemon. Its main flowering season is March to July, with fruits starting to form in May, but, as its name implies, it flowers and fruits lightly throughout the year. At almost any time, you’ll have the faint scent of a few flowers, and a lemon to pick for the kitchen. The younger growth of this variety is pretty and tinged red, so the plants also have an elegance. They will reach a good 6ft or 7ft when fully grown, with a pom-pom of light green leaves nearly 5ft across.

It’s now, as its main flowering season starts, that you can have a real lemon binge and harvest last season’s fruit, which will often drop if left on the tree. I love eating them — as you would in Sicily — in an early spring garden tempura, mixed with new-season carrots and spring onions, or combining them with blood oranges, chicory and walnuts for a zippy, body-spring-clean sort of salad (see recipes).

The calamondin orange is ideal for the non-specialist citrus grower. This slightly smaller tree is fairly easy to grow and fruits and flowers throughout the year. It is one of the most decorative of the citrus family, with lots of small, bright tangerine-coloured fruits. These are bitter eaten straight from the tree, but make fabulous marmalade.

I’m also keen on growing a kaffir lime, whose leaves, more than its knobbly green fruits, are invaluable for cooking. You can use their zest and juice, but it’s the large, double leaves that are so aromatic. The taste is reminiscent of lemon grass, but stronger and with a hint of ginger, ideal for all sorts of oriental curries, soups and stir-fries. Kaffir limes are fairly easy to grow, but will need a slightly higher winter temperature than the lemon or calamondin, ideally above 12C (54F). Limes make slightly smaller trees than lemons, growing to about 5ft tall and with a more compact leafy top.

The Tahiti and the orange-fruited sweet limetta are the limes to grow for the classic fruits. Tahiti limes flower in spring with fruits ripening throughout the summer; they have a good flavour and are zesty, juicy and seedless. Limetta is an amazing deep red-orange when fully ripe and is sweeter than most limes, so you can eat it whole as well as using it as a normal lime. The individual fruit don’t get as big as Tahiti, but it is more productive.

The final citrus to think of growing is the commercially grown sweet navel orange, but this needs all-year-round warmth, so will grow well only in a heated greenhouse. This has the most fragrant blossom in spring and the stems — unlike most citrus varieties — tend to be thornless. The fruit ripen to orange in late autumn when temperatures drop below 15C (59F) and are probably the most delicious of all – seedless, huge, sweet and juicy.

The shops are full of all these fruits in their prime at the moment, but why not go one step further and grow your own?

Tips for success with citrus

1 All citrus like a high humidity, so stand plants in trays of gravel filled with water, and mist regularly. This will help to control red spider mite. Water regularly from March to November, but don’t overdo it as the roots rot easily. Wait until the topsoil looks dry — it is best to water little and often, especially in the winter, when the tree is semi-dormant. Use rain water if your tap water is alkaline.

2 Feed every week in summer to promote flowering and encourage healthy foliage. There are specialist summer feeds (high nitrogen, plus trace elements such as iron, which citrus need), and a different winter mix (lower nitrogen content) to use from October to March, every two to four weeks, depending on the weather. It’s well worth finding these at a specialist nursery.

3 Hardiness varies between varieties, so check the cold tolerance of your plant. Trees grafted on to Poncirus trifoliata rootstock have increased cold tolerance. Most varieties will take some frost but not prolonged cold. Put outside for summer (but keep out of the wind, which can be death to any citrus tree) and bring inside for winter, ideally keeping them above 5C (41F).

A key with all citrus is lots of natural sunlight, so they’re happiest grown in a frost-free (or slightly warmer) greenhouse or conservatory through the winter, and being moved out to the garden as soon as the frosts are over, to return inside only when it gets cold at night in September or October. If you don’t have a greenhouse, try to find them a winter spot with overhead rather than side light and good ventilation. If they are stored in a cold greenhouse, wrap them in fleece on cold nights. This will prevent flower and fruit drop.

4 Remove dead branches and shoots growing from below the graft level and prune in spring, removing water shoots. These are much softer and fleshier than the rest. Too many water shoots will take energy from the older wood, where flowers and fruits form.

5 The main pests of citrus trees are sap-sucking scale insects and mealy bugs. Use biological control to avoid (visit defenders.co.uk for advice on natural pest control) and treat at the first sign of a problem, shown by a sticky black coating on the leaves. Use a cotton bud dipped in methylated spirits or simply wash with soft soap.

Cross Common Nursery, Helston, Cornwall (01326 290722/290668; crosscommonnursery.co.uk)