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Kumquat: How to Grow – Fruit of the Month

Kumquat,
Citrus japonica,
Flora Japonica, 1870,
Kurt Stober's Online Library ,
Kumquat
Citrus japonica
Flora Japonica 1870
Kurt Stober’s Online Library

Kumquat stats/requirements at a glance

Ease of Raising: 3/5 Bi-weekly check-ups
Water: 3-4/5 Every 2nd day to Daily
Sun: 5/5 Full sun
Training: 3/5 Some, pinching out growth or flowers
Fertilise/Feeding: 3/5 Moderate, monthly
Time to Harvest: 5/5 Forever, 5+ months
Frost Hardiness: 4/4 Very hardy, can’t cope with black frost
     
Uses Culinary  
Most Problematic Nemesis: Caterpillars  
Container Plant: Yes, ideal for containers  

Quick intro  

The kumquat citrus is known for its frost hardiness. It is a truly fantastic member of the citrus family and is a joy to have in the garden. The little sour fruits make excellent additions to jams, jellies and marmalade – or to eat if you like sours 😆

History  

It is native to south Asia and the Asia-Pacific region. The earliest known historic records date back to the 12th century, China. It was first introduced to Europe in 1846 and soon after brought to North America.  

Science Stuff  

The citrus and its hybrids belong to the Rutaceae family, which includes roses, raspberries, and blackberries. The kumquat, Citrus japonica, is a single species with many variants, such as the Marumi/Morangu (round), Nagami (oval), Meiwa, Hong Kong, Jiangsu and Malayan kumquat. The calamondin another small citrus and member of the Citrofortunella genus, but is an intergenic hybrid between the tangerine (Citrus tangerina) and kumquat (Citrus japonica).

Other hybrids include:

  • Calamansi: mandarin orange x kumquat
  • Citrangequat: citrange x kumquat
  • Limequat: key lime x kumquat
  • Orangequat: Satsuma mandarin x kumquat
  • Procimequat: limequat x kumquat
  • Sunquat: Meyer lemon x kumquat
  • Yuzuquat: yuzu x kumquat
Kumquat flower buds
Citrus japonica

Growing Kumquats  

Most citrus grow well in Mediterranean-type or subtropical climates, they do not fare well in very humid climates and will require additional watering in more arid environments. The increased frost hardiness and moderate drought-tolerance of the kumquat (and other Citrofortunella) is a big advantage in arid or inland regions that are prone to frost.   This evergreen tree produces new growth in spring followed by flowers. The fruit develop and remain green for most of the year and all the fruits will ripen towards late winter for one large batch of kumquat fruits. Once the tree has acclimated and established in the garden it is drought-tolerant and a prolific producer, it can produce over a kilogram worth of kumquats each winter.  

You can fertilise the citrus about once a month or when the water in the pot saucer runs clear (this is usually a good indication for some fertilisation, because brown pot water is indicative of nutrients in the water). Some minimal pruning will be needed to keep the general shape and prevent crisscrossing branches. Cut out dead or damaged parts to promote new growth.

Pests and disease  

Citrus swallowtail caterpillars can be a problem – just be on the lookout for black and orange caterpillars on your plant, they will eat both leaves and fruit rinds. You can dispose of them or collect them to feed for the birds or chickens! Here is my full Pest Profile on this caterpillar (and some others).

During winter when the plant immunity is low, scale bugs can be a bane of all citrus members. The best way to control scale is by giving the tree a good scrub with soapy water and a soft brush, you can read more about these pests on the Profile Post for Scale Insects. Also check out my environmentally friendly pest control recipes!

Citrus swallowtail worm caterpillar two immatures, Papillio demodocus
Citrus Swallowtail Caterpillars (immatures)
Papillo demodocus

Other Kumquat Tips  

I grow a ginger mint in the same pot as the kumquat – it was a bit of an experiment to see whether the scale (or their ant farmers) would want to be in a pot full of strong smelling mint. I haven’t had any scale problems on the kumquat thus far, whether this is because of the mint or the resistance of the plant I am not sure, but I thought it would be worth the mention 😎

Harvesting & Storing  

The plants produce perfect and imperfect flowers which have a lovely strong aroma. The fruits are harvested once fully coloured (light orange) and we eat them peel on, but the peels come off very easily. Harvest ripe kumquats with a pair of secateurs/scissors to prevent damaging the tree. The rind can be bitter and the fruit is more sour than sweet and they have a very aromatic flavour to them akin to the flower, making them ideal for adding flavour to desserts (icing). The fruits will keep for a while (about two weeks) once picked, but it is better to leave them on the plant until needed and picked well before spring.   

Kumquat fruits from development to harvest
Citrus japonica
Kumquat fruits fully ripe
Citrus japonica

Propagation  

The kumquat, as most other citrus, can be propagated through grafting or cuttings in spring and autumn. Seeds can be unpredictable and some take up to a month to germinate.

My Kumquat  

My kumquat has been in the garden since 2016, producing flowers and fruits during its first spring. It was a small tree due to its pot bound nature, however I have recently planted it out into the main garden (early 2019) and it should bulk up a bit more now. It is a very easy going plant and when in flowers it fills the garden with its amazing smell.   

Kumquat tree
Citrus japonica

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