A tasty, hardy and ornamental calamondin orange
Another citrus which seemed to have enjoyed the rains, and now looks more prosperous than ever, is a variegated citrus cultivar I picked up at the Khamtieng flower market downtown Chiang Mai. Originally I planted it with the sole purpose to use its sour immature green fruits when experimenting with the miracle fruit. However, the abundant fruit production of this citrus made me taste a yellow mature fruit – really nice! The fruit’s juice is a wonderful addition to a glass of drinking water and the fruits are sometimes used in Thai cooking as a substitute for lime (although my Thai family detests it).
Many people have asked me what it is, and even collected seeds for their home plantations. I have always dismissed it as an ‘ornamental citrus hybrid’, but due to its superior characters I have recently devoted plenty of time to track down what it really is. First, I wish to make a very condensed summary about what some of the ordinary citruses/oranges are:
Pure original species (genus Citrus, family Rutaceae):
Citron (Citrus medica), native to northern India.
Variety ‘sarcodactylis is also called ‘Buddha’s hand’, the mascot of Dokmai Garden.
Kaffir lime/papeda lime/leech lime/makrut lime (Citrus hystrix), native to Malaysia.
Kumquat (Citrus japonica =Fortunella japonica=F. margarita) native to S. China.
Mandarin/tangerine/satsuma/clementine (Citrus reticulata), native to subtropical China.
Pomelo (Citrus maxima), native to Southeast Asia.
Crosses between species:
Lime (Citrus x aurantiifolia)
A cross between citron (Citrus medica) and kaffir lime (C. hystrix).
Lemon (Citrus x limon)
A cross between citron (Citrus medica) and orange (Citrus x aurantium).
Orange (Citrus x aurantium)
A cross between pomelo (Citrus maxima) and mandarin (C. reticulata).
Grapefruit (C. x aurantiifolia Grapefruit group)
An orange back-crossed with female pomelo (Citrus maxima).
Limequat (Citrus x floridana)
A cross between kumquat (C. japonica) and lime (C. x aurantiifolia).
Calamondin or calamansi (Citrus x microcarpa= X Citrofortunella microcarpa)
A cross between kumquat (Citrus japonica) and mandarin (Citrus reticulata).
So, what do we have at Dokmai Garden? The seeds’ interior green colour suggests kumquat genes, but a pure kumquat is not growing in this upright manner. A limequat is usually egg-shaped, our fruits are more mandarin-like. A calamondin (from Tagalog ‘kalamunding’) has indeed upright growth and flattened (when mature) fruits easy to peel like a mandarin. It turns out there are at least three names for a variegated calamondin: ‘Variegata’, ‘Tiger’ and ‘Peters’. If these names refer to different cultivars, or to the same, I do not know, but in conclusion I should say that our variegated citrus is a ‘Variegated calamondin’ Citrus x microcarpa ‘Variegata’.
If you wish to grow it, and you should, make sure it has full sun for abundant flower and fruit production, and water it generously but without causing water logging. I do not know if seedlings work well, as most commercial citruses are grafted onto hardy rootstocks.
The name ‘Kumquat’, one of the calamondin’s parents, is derived from ‘chin kan’ (Chinese) and ‘kin kan’ (Japanese) meaning ‘golden yellow’. For a while it was split from the genus Citrus and given the genus name Fortunella, and many kumquat cultivars were named as separate species. Thanks to molecular analyses of the plants’ genome (DNA) we are back to the original concept; there is only one species, Citrus japonica, described by the Swedish botanist Carl Peter Thunberg in 1784.
In this context it is relevant to consider what a species is? The old concept was that a stable morphological form was enough to describe a species with a scientific name. That resulted in a myriad of species, and still do for fossils such as within the genus Homo. The modern biological species concept is a group of interbreeding individuals, meaning that two specimens which can not be crossed belong to different species. With molecular analyses we can look into the genomes and learn whether there are geneflows between populations or not, and make pedigrees, using a technique not too different from fatherhood analyses of human babies. This technique is not applicable on fossils and so the field is open to endless publications of ‘new species’.
The biological species concept works well for mammals and birds, but it gets more complicated for plants, where even members from different genera can be crossed. It is decided though that natural genetical barriers such as pollinators’ preference separate different species, although the gardener can cross orchid species like crazy and create fantastic or monstrous unnatural plants.
If we go to bacteria, they may be considered one super species since seemingly different individuals may still exchange genetic material. The citruses are similar in the respect they can all be crossed. Based on this fact one might argue there is only one citrus species. However, geographical barriers to gene flow (crossings) have allowed local populations, confirmed by molecular analyses. Such local populations are considered species. In my opinion, a ‘species’ is a man-made concept and you come to a point when you have to determine, not explore, what a species is. Some biologists furiously contradict me and argue that the species concept is a discovered reality, not invented. Such biologists are usually specialists on small organism groups where problematic cases such as bacteria and citruses do not occur. The need for scientific species names is to allow exchange of information about certain organisms, in the 18th century of economical and medicinal reasons, today also of ecological reasons.
Ultimately, life on Earth constitute more or less related individuals, and to facilitate our language we may group certain individuals into citruses, wasps, Swedes, boletes, species….
To further complicate the question, what is an individual? An aspen tree may create many more individual trees from root shoots, cloning itself. Is a genetically homogenous aspen stand to be considered one or several individuals? When a variegated calamondin appears as a mutation in a non-variegated calamondin bud, resulting in one branch being variegated and genetically different from the rest of the tree (a so called ‘sport’), is that now another individual, or does it become an individual when detached and rooted? It is a matter of definition.
I thank James Wearn at Kew Gardens for kindly communicating with me on this matter, and for further information you may want to consult:
Text & Photo: Eric Danell