Citrus


(Genus: Citrus sp. - Family: Rutaceae)

 

Citrus trees and their origins

Citrus is the group name and genus of a family of fruits which includes the orange, lemon, lime, tangerine, Clementine, grapefruit and mandarin.  Originating in Asia and dating back to ancient times, they were first documented in 2,200 BC. 

The home of all citrus fruits is India with some varieties stretching into the Far East.  Cedar was first introduced to Europe by Alexander the Great and when the Crusaders arrived in the 11th century, the brought with them bitter oranges and lemons.

It is unclear how many true species exist in the citrus genus, as many are, in fact, hybrids. 

 

How to plant citrus trees

Given the right climate, these hardy evergreens are relatively easy to grow. Citrus typically enjoy a warm climate and are frost tender.  Temperatures should range between 13oC – 30oC; below this will damage the crop and potentially lead to the death of the tree.  However, citrus are suitable for growing in pots and if they can be overwintered and protected from frosts, it is possible to grow them in cooler regions. 

Oranges, lemons and limes, in addition to other citrus plants should be planted in early spring outdoors, after the threat of frost has passed.  If placing in a container, they can be planted closer to summer. 

The soil should be rich in nutrients, as citrus plants enjoy feeding.  Place them in a medium textured soil that is deep, well drained and prepared with organic matter.   Avoid heavily clay-based or chalky soils. 

Citrus require lots of space to grow, place each planting hole 15-25 m²apart. 

Fertiliser is essential and should be applied in late winter during the dormant period using xxxxx or xxxxx xxx xxx-dose g per plant, depending on its age, until the tree is in its 4th year.  In year 5, apply 2-3kg of the fertiliser per plant.  Alternatively you can use xxxxx every 2-3 months.

Initially, when transplanting the orange, lemon or lime trees use these fertilisers at a dose of xxx-xxx g per hole and mix well.

To avoid iron chlorosis, leaf yellowing during the dormant phase or if the soil is chalky, distribute a dose of xxx microgranules which is iron chelate based, at a dose of xx-xxx g / plant and repeat 2 -4 treatments, one every 10-15 days.

Citrus require lots of moisture to grow, especially in summer, however, they are demanding in terms of the quality of water.  The water cannot have a high concentration of boron, sodium, and especially chlorine, which is present in drinking water.

In years where you expect a high crop yield, it is necessary to thin out the fruit in order to maintain a high level of quality.  During the first 4 years, avoid pruning, only when essential, to ensure that the tree develops a strong structure.  In the 5th year, prune carefully after the harvest and before flowering begins, always keeping in mind that all citrus trees bear fruit on wood from the previous year. 

Orange pruning may only be required every other year while lemon, lime and tangerine should be completed annually to avoid alternate fruit bearing.

 

When to harvest Citrus?

Citrus fruits are cultivated plants belonging to several genera, of which, the key three are Citrus, Fortunella and Poncirus. The first contains many of the key citrus fruits: orange (C. sinensis), lemon (C. limon), mandarin (C. reticulata), clementine (C. Clementine), Mandarin tangerine (C. tangerina ) and grapefruit (C. paradisi).

A lemon or orange tree can grow up to 9m high and features leaves that are lancelet and leathery, they can remain on the tree for over 2 years. Their colour varies from dark green to yellowish green depending on the age of the leaf.

These citrus trees are in bloom from February to March with beautiful and delicate orange blossom which comprises of 5-petal flowers, ranging in size from 1-5cm and is white in colour.    Following the flowering period, the fruits begin to develop and reach maturity between autumn and spring of the following year. 

Citrus fruits are harvested when ripe, as they are not capable of ripening further after harvest, except for the lemon, which continues to ripen.  The fruits are berries, round or oval in shape with a thick, brightly coloured skin and filled with a pulp that is swollen with watery juice.  

Consume when oranges, lemons, limes and other citrus fruits when fresh. 

 

Propagation of citrus trees

Citrus plants can be propagated in a number of ways; you can grow from seed, by cuttings or choosing a good rootstock.  Traditionally, most orange, lemon and lime trees are slow-growing, which is why many gardeners opt for mature plants.  Citrus grown from seed can take many years to mature and bear fruit, this fruit can also be inferior to the original plant.  

When choosing a cultivar, choose a rootstock that is suited to the local conditions and your soil. Choose one that will have a good vigour but also a high quality fruit production. 

 

Diseases and insect affecting citrus:

  • Mealybugs
  • Serpentine leafminer
  • Aphids
  • Flies
  • Fitoftora
  • Anthracnose

 

Did you know?

Citrus fruits are used in all types of cooking from sweet to savoury dishes.  They are a feature in jams, sauces, cakes, dressings, soups juices and are used widely in different global cuisines from Latin American through to Asian. 

They are an important addition to any diet as they are such a rich source of vitamins C and P. The daily requirement of vitamin C is 60mg which rises to 100mg for smokers because smoking eliminates this vitamin more rapidly and increases the production of free radicals.

An orange contains 25 to 80mg of vitamin C per 100g; this is useful in the prevention of deficiency diseases such as scurvy and also useful when the body is fighting infection as the immune system consumes more vitamin C during this time.

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