Kumquat – Fortunella

Palm Centre – Plant of the Month – November  2007

Kumquat – Fortunella

This month we’d like to introduce you to a plant grown for the past 150 years in Europe, America and Asia, from where it hails, as both a decorative plant and a source of fruit.  It has only recently been introduced in Turkey but is already becoming popular.  It has an exotic appearance as a decorative plant, and provides tasty fruit and, it would seem, is the citrus fruit most able to withstand low temperatures.

Originally placed by botanists within the citrus family in 1915 it was reclassified by Dr Walter Swingle as a member of the Fortunella family which is a group of five types of kumquat plants all found in Asia.  In Chinese the kumquat is known as ‘Golden Orange’.

The kumquats all come from southern China and Malaysia and were first exported as decorative plants in the second half of the nineteenth century: initially to Europe, and then to North America before becoming known in other parts of the world.

The kumquat tree is a slow-growing, compact tree reaching a maximum of 3 – 4.5 metres in height.  When young it has greenish-coloured, curved branches without thorns or sometimes with small thorns.  Its leaves are a tapering oval in shape, with very slightly serrated edges, dark green with a paler green on the underside.  Depending on the variety the fruit can be round or oval and golden yellow to a reddish orange in colour.  Fruits have 3 – 7 segments, are acidic, not very juicy and can be seedless or may have seeds.  Fruits can be eaten whole without peeling.  In general the tree flowers in the summer, fruits start to ripen towards the end of autumn and, if not picked, will stay on the tree the whole winter.

Fortunella hindsii – Hong Kong Wild: this variety is found in the wild in Hong Kong and has round fruit, with radii 1.5 – 2cm.  Whilst it is grown for its fruit in China it is a really thorny plant and, outside China, is only grown in pots as an ornamental.

Fortunella japonica – Marumi or Round Kumquat:  fruits are round with a radius of 1.5 – 2cm.  This tree can reach a height of 2.5 – 3 metres.  It resembles the Nagami variety (see below) but has more thorns.

Fortunella crassifolia – Meiwa or Large Round Kumquat: again round fruits with a radius of 4cm, orange in colour, and several seeds in each fruit.  This is a dwarf tree with no thorns or some very small thorns.  Of all the kumquats this one gives the best fruit for eating from the tree.  Fortunella crassifolia ‘Sun Stripe’ is a Japanese hybrid with variegated leaves and yellow fruit with green stripes –a very ornamental plant.

Fortunella polyandra – Malaysian Kumqaut: cannot be found in Turkey.

Fortunella margarita – Nagami or Oval Kumquat: the variety most grown both internationally and in Turkey.  This tree can reach 4 metres, has oval fruit 4 – 5cm in length, 2 – 3 cm wide and orange in colour.  It is said to be the hardiest citrus withstanding temperatures down to -120C.  It can be grown purely as an ornamental or for its fruit.

Kumquat fruits, as they can be eaten whole, without removing the peel, make a colourful and tasty addition to cocktails, and can also be used to make marmalade or syrup.  The Chinese make a sauce of kumquats, orange juice, honey, salt and butter which can be used in many ways.  Kumquats can also be used to produce sweet pickles.

Kumquats can be grown from seed or cuttings but the most reliable method of propagation is by grafting on to good rootstock.  The preferred rootstock is Poncirus trifoliata, Japanese Bitter Orange, and kumquats produced by this method are very well suited to container growing: they are more compact and grow more slowly.   If grafted to orange rootstock larger, faster growing, plants are produced but the compact form is spoiled.  If you have alkaline soil then grafting on orange rootstock produces stronger plants.

Kumquats are not fussy about soil.  Whilst they prefer a permeable soil they will also grow in clay soils.  They prefer direct sunlight but will also grow in the shade of larger trees.  They must be watered in summer.  In our Mediterranean region between June and September it may be necessary to treat them against leaf moth – a monthly application of ‘Mospilan’ or ‘Muadili’ should be effective.

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