Following a long history of cultivation, coupled with the ease by which hybridisation can occur within the genus Cistus, it has become very difficult to devise a workable taxonomy for all the commercially significant taxa, Previous systems have recognised anything from 1 - 167 ‘good’ species in the genus. Work is ongoing to produce a workable monograph of the genus and in the meantime we are following the the treatment proposed by D.J. Mabberley (A classification for edible citrus: an update, with a note on Murraya (Rutaceae), in Telopea 25: 271-284, 2022).
The parentagege of Citrus × limon is (male) Citrus medica × (female) Citrus × aurantium

Common Name: Lemon

General Information

Citrus × limon is a spiny, evergreen shrub or small tree growing 3 - 6 metres tall[].
A very popular fruit with a wide range of uses, the plant has been under cultivation for at least 1,000 years, having been first recorded in China around 1,000 AD[]. It is widely grown for its edible fruit in warm temperate to tropical zones[, ].

Known Hazards

None known

Botanical References

Range

Original range is obscure, possible Asia.

Habitat

Original habitat is obscure, probably a hybrid involving C. medica x C. aurantifolia[].

Properties

Edibility Rating
Medicinal Rating
Other Uses Rating
Habit	Evergreen Shrub
Height	3.00 m
Growth Rate	Medium
Pollinators	Apomictic, insects
Self-fertile	Yes
Cultivation Status	Cultivated

Cultivation Details

Three main climates are suitable for commercial citrus production - tropical climates, subtropical with winter rain such as in the Mediterranean and semitropical with summer rainfall as found in Florida and southern Brazil[]. The optimal temperatures for citrus cultivation range between 25 - 30°c, with the coldest month having an average minimum of at least 15°c[]. Growth generally ceases below 13°c and above 38°c[]. If there are dry periods of more than three months, then irrigation will be necessary[].
Prefers a moderately heavy loam with a generous amount of compost and sand added and a very sunny position[, ]. Prefers a pH between 5 and 6[]. Tolerates a pH in the range 4.8 to 8.3. Plants are intolerant of water logging[]. When growing plants in pots, a compost comprising equal quantities of loam and leafmould plus a little charcoal should produce good results[]. Do not use manure since Citrus species dislike it[]. When watering pot plants it is important to neither overwater or underwater since the plant will soon complain by turning yellow and dying. Water only when the compost is almost dry, but do not allow it to become completely dry[].
The lemon grows better in the subtropics than in the tropics[]. Dormant plants can withstand temperatures down to about -6°c so long as this is preceded by a spell of 2 - 3 weeks of cool weather to allow the plant to acclimatize[]. If the change from mild to cold weather is more sudden then the plant will still be in growth and will be much more susceptible to damage and can be harmed by temperatures below 0°c[]. The young growth in spring, even on mature plants, is frost-tender and so it is best to grow the plants in a position sheltered from the early morning sun[]. It is best if a winter minimum of 4°c is maintained[].
There are many named varieties[, ].
By budding onto hardier species such as C. Aurantium, C. Ichangensis or Poncirus trifoliata, the lemon becomes more cold tolerant and its climatic range can be somewhat extended[].
The flowers are sweetly scented[].
Plants dislike root disturbance and so should be placed into their permanent positions when young. If growing them in pots, great care must be exercised when potting them on into larger containers[].

Edible Uses

Fruit - raw or cooked[, , ]. A very acid taste[]. Mainly used as a drink and as a flavouring[, ]. It is also used in salad dressings etc where it acts as an antioxidant as well as imparting an acid flavour[]. The juice is used to help set jam[]. The fruit can be up to 15cm long and 7cm wide[].

The dried rind of the fruit is often used as a flavouring in cakes etc[, , , ].

The dried leaves are sometimes mixed with tea leaves for use as a flavouring[].

An essential oil from the rind is used as a food flavouring[, , ].

The flowers are eaten in ice creams, fritters, jams etc[].

Medicinal

Lemons are an excellent preventative medicine and have a wide range of uses in the domestic medicine chest. The fruit is rich in vitamin C which helps the body to fight off infections and also to prevent or treat scurvy[, , ]. It was at one time a legal requirement that sailors should be given an ounce of lemon each day in order to prevent scurvy[]. Applied locally, the juice is a good astringent and is used as a gargle for sore throats etc[]. Lemon juice is also a very effective bactericide[]. It is also a good antiperiodic and has been used as a substitute for quinine in treating malaria and other fevers[].

Although the fruit is very acid, once eaten it has an alkalizing effect upon the body[]. This makes it useful in the treatment of rheumatic conditions[].

The skin of the ripe fruit is carminative and stomachic[].

The essential oil from the skin of the fruit is strongly rubefacient and when taken internally in small doses has stimulating and carminative properties[].

The stem bark is bitter, stomachic and tonic[].

An essential oil from the fruit rind is used in aromatherapy. Its keyword is 'Refreshing'[].

Citrus species contain a wide range of active ingredients and research is still underway in finding uses for them. They are rich in vitamin C, bioflavonoids, acids and volatile oils. They also contain coumarins such as bergapten which sensitizes the skin to sunlight. Bergapten is sometimes added to tanning preparations since it promotes pigmentation in the skin, though it can cause dermatitis or allergic responses in some people[]. Some of the plants more recent applications are as sources of anti-oxidants and chemical exfoliants in specialized cosmetics[].

The bioflavonoids in the fruit help to strengthen the inner lining of blood vessels, especially veins and capillaries, and help counter varicose veins and easy bruising[].

Other Uses

A semi-drying oil obtained from the seed is used in soap making[, ].

An essential oil from the peel is used as a food flavouring and also in perfumery and medicines[, , ]. A higher quality essential oil is obtained from the flowers[]. The peel contains 0.4% essential oil[].

An essential oil obtained from the leaves and young twigs is called 'petitgrain oil'. Yields are around 0.4%[].

The dried fruit rind has been used as an insect repellent in the clothes cupboard[] and also in potpourri[].

The juice of the fruit is used for polishing bronze and other metals that have been neglected[]. It can also be used for removing ink stains[]. The juice is used as a bleaching agent[].

Wood - nicely veined, it takes a beautiful polish[].

Propagation

The seed is best sown in containers as soon as it is ripe, after thoroughly rinsing it[, ]. Sow stored seed in containers as soon as possible]. Germination usually takes place within 2 - 3 weeks at 13°c. Seedlings are liable to damp off so they must be watered with care and kept well ventilated. The seed is usually polyembrionic, two or more seedlings arise from each seed and they are genetically identical to the parent but they do not usually carry any virus that might be present in the parent plant[]. When large enough to handle, prick the seedlings out into individual pots and grow them on until they are 10cm or more tall before planting out into their permanent positions.
Cuttings of half-ripe wood, July/August in a frame. This species grows easily from cuttings[].
Layering in October.

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