Common Name: Pummelo

General Information

Citrus maxima is a low-branching, evergreen tree growing 5 - 10 metres tall with occasional specimens up to 15 metres[]. The spreading branches bear spines up to 5cm long, though there are some forms in cultivation that are free of spines[].
The tree is widely cultivated for its edible fruit in tropical and subtropical regions and, even if the fruit is of inferior quality, the tree may still be grown for its various medicinal applications[, ]. It is an especially popular fruit in Thailand where a range of excellent quality cultivars have been developed[]. These forms are usually small trees with a spreading habit; fruit with thin rind and firm, crisp flesh, not very juicy; fruit often seedless or with shrivelled seed[].

Known Hazards

None known

Botanical References

,

Range

E. Asia - Malaysia.

Habitat

Not known in a truly wild situation[].

Properties

Edibility Rating
Medicinal Rating
Other Uses Rating
Habit	Evergreen Tree
Height	6.00 m
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[]. In the production centres of Thailand mean monthly temperatures are about 25 - 30°c with a few cooler (and dry) months; the dry season lasts for 3 - 4(-5) months and annual rainfall is about 1,500 - 1,800mm[]. The crop is not grown commercially above elevations of 400 metres[].
Prefers a deep, well-drained but moisture-retentive loamy soil in full sun[]. Prefers a pH in the range 5 - 6[].
In the tropics the trees flower 2 - 4 times per year, mainly in conjunction with shoot growth flushes[]. The main flowering period follows the onset of the monsoon rains, unless it is brought forward by irrigation[]. A load of growing fruit limits fruit set from subsequent blossom periods[]. Some fruit is usually available throughout the year[].
Yields greatly depend on cultivar and environment, but there appears to be no reason why the potential yield of pomelo should be lower than for other citrus species[]. Thai sources put yield at 70 - 100 fruit per tree per year, equivalent to the 20 t/ha per year reported as a good yield in Malaysia[].
The white flowers are fagrant[].

Edible Uses

Fruit - raw or cooked. The pulp is somewhat acid, but very tasty[]. Excellent to eat out of hand, the fruit can also be added to fruit salads or make into jams, marmalade etc[]. The fruit is large and thick-skinned, resembling a grapefruit but with a firmer, non-bitter flesh and less juice[]. The fruit is 10 - 15cm in diameter, occasionally up to 30cm[, ]. Individual fruits have been known to weigh up to 8 kg[].
The fruits are utilized as a source of pectin[].

The peel can be candied and used as a flavouring in cakes etc[].

The flowers are used for scenting tea[].

Medicinal

Various parts of the tree have traditional medicinal applications, including the leaves, flowers, fruits and seeds. They are used to treat a range of conditions, including coughs, fevers and gastric disorders[].

A decoction of the fresh leaves, in combination with the leaves from some other aromatic species, is used in the treatment of coryza, influenza and headache by inhalation of the vapour from the boiling decoction[].
A massage using the heated young leaves is an effective treatment for bruises[]

The fruit rind is an effective treatment for dyspepsia, colic and cough, in a daily dose of 4 to 12g in the form of a decoction[].

The seed envelopes contain pectin, which is a haemostatic[].
The seeds, stripped of their envelope and charred, are applied externally as a treatment for impetigo[].

Other Uses

An essential oil is obtained from the flowers[]. The aromatic flowers are used to make perfume in Vietnam[].

The leaves are put into the bath water to add a refreshing aroma[].

The wood is used for tool handles[].

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 polyembryonic, 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[].
Air layering.

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