Citrus: sweet and sour by Malcolm W. Campbell BA, MAIH, MIPPS.

You might have wondered why limes are sold green yet they colour to yellow if left on the tree. I suppose we're so conditioned to 'lime green' in our colour language, that we don't question it much, but if a lime is left to ripen to its natural yellow on the tree, it quickly develops "Stylar-end Rot", which turns the fruit brown at one end. That wouldn't look too flash on the greengrocers' shelves, but it still juices quite well! Grow your own limes and the trip between tree and table is not much of a problem. A fresh lime soda on a hot summer's day has got to be one of the home gardener's greatest delights. That's if you're not an amber fluid imbiber and even then the Mexicans prefer a slice of lemon and a dash of salt with their beer.

Limes are a misunderstood citrus. Put aside as the Cinderellas of the clan and frequently in the company of the kumquat and calamondin, they are variously given all sorts of names and this has led to great confusion with home gardeners. I've seen and heard the "Tahitian Lime" Citrus latifolia called "Macedonian" lime (Greek or Slavic origin uncertain), "Persian" lime and "Bearss" lime.

"Tahitian Lime" is the "Lime of Commerce" and the fruit from which those products that still use real limes in their manufacture, resort to as the fruit of their first choice. It is seedless and offered to home gardeners in South Australia grafted onto "Rough Lemon" rootstocks. Although growing on a "Rough Lemon" root system makes the tree tolerant of alkaline clay soils, it means that it keeps growing, flowering and setting fruit, all year round, just like most 'Lisbon' lemons growing in Mediterranean areas, since they are usually grafted onto "Rough Lemon" rootstocks too. So what you might ask? Well that makes the "Tahitian Lime" in particular susceptible to being frost damaged in winter in areas where frost is likely. The 'Lisbon' lemon is hardier than the "Tahitian Lime" in that respect and generally recovers after even quite a heavy frost of say -4_C. In frost prone areas a better "Tahitian Lime" is grown on "Trifoliata" rootstock which is Poncirus trifoliata, or its hybrid "Flying Dragon", where the root system stops growing in winter and so does the scion canopy. This means that the foliage is tougher and more mature, because it hasn't been growing with soft lush leaves in the cold period and that makes the tree less prone to frost damage. All limes need protection from the wind, so if you live on the foreshore, your lime's best chance at survival is around the back in a more protected area. All limes are considered cold sensitive, but the "Tahitian Lime" is the toughest if grown on the above recommended rootstocks. is the "Lime of Commerce" and the fruit from which those products that still use real limes in their manufacture, resort to as the fruit of their first choice. .

"West Indian Lime" is for those who live in a warm frost free area, humid or even tropical. You can grow it from seed and it is notable in that its fruits are smaller and less juicy than the "Tahitian Lime". For those who garden in the sub tropical and tropical areas, look out for the thornless clones of the "West Indian Lime", unless you are establishing a villain-proof hedge!
For our frost prone gardeners, look to the kumquats (and the spelling cumquat is also equally valid), calamondin and tangelo for hardy varieties. But if it's the tangy lime flavour you want, then the hybrids such as the 'Rangpur' and 'Kusaie' are by far the most cold tolerant of the lime-tasting citrus. is for those who live in a warm frost free area, humid or even tropical. You can grow it from seed and it is notable in that its fruits are smaller and less juicy than the "Tahitian Lime".

'Rangpur' lime is instantly recognisable as it has a more Mandarin character and orange coloured fruit with very distinctive green seeds, a mild flavour, but still very tasty and a recognisable lime note or fragrance.

'Kusaie' lime is a yellow fruited form of 'Rangpur' and is generally smaller than the "Tahitian Lime". It is certainly more cold resistant. Its flavour is quite astringent and to my taste buds, a real wild lime flavour. In common with all the varieties mentioned here they make an excellent and productive small tree in a half hogshead, which if you don't live in a wine-growing area, is the name given to an oak wine barrel. Both 'Rangpur' and 'Kusaie' fruit all year round, but with one main crop in summer. They are both quite cold resistant and tolerant of Tristeza virus, which is so effectively spread by the prolific vector that we often spot on citrus, the "Black Aphis" Aphytis citricidus. lime is a yellow fruited form of 'Rangpur' and is generally smaller than the "Tahitian Lime".

"Kumquat" or "Cumquat" are widely grown as container plants and to my frequent surprise there are not enough of the edible ones being grown. You can still have a charming kumquat and an edible variety in the same plant. They are all much more cold tolerant than the limes.

'Nagami' kumquat is Fortunella marginata and has oval-shaped fruits and is the most widely grown kumquat in the USA, China and Japan. It has a sweet skin with a deep orange colour, that makes wonderful dried fruit due to the high oil content in the peel. The leaves are larger than other kumquats which instantly sets it apart and the distinctive fruit shape, make it a memorable kumquat and a pretty tree.

'Marumi' kumquat is Fortunella japonica, and is by far my favourite. It has small round fruit and a much sweeter tasting fruit than 'Nagami', but both have edible skin. They can also be dried and prepared as glacé. Noëlle Tolley was busy preparing some dried and glazed Kumquats made from 'Marumi' when I called on her Renmark SA kitchen recently. She markets them mainly to speciality gourmet shops and a few discerning hotels in Melbourne and Sydney. They make a lovely snack as exquisite sweets served either fresh with cream or preserved in a brandy-liqueur base for a few years. My Chinese Acupuncturist, Dr Kang at Plympton SA, swears by the crystallised kumquat as an aid for people to eat, if they are trying to give up smoking. That's never been my problem, by the way. 'Marumi' is a smaller and less vigorous kumquat than 'Nagami' but I find its leaves arranged in such a delightful way that it would appeal even when not carrying its prolific fruit set.

"Calamondin" is Citrus madurensis and looks like a kumquat and is not surprisingly mis-represented as such, quite frequently. The variegated form is particularly attractive and even has variegated fruits, but the stripes disappear as they mature. Both the standard green and the "Variegated Calamondin" have a very productive fruit set that can be used in the same way as the other edible kumquats, for preserves and drying.

"Kaffir Lime" Citrus hystix, (syn. "Mauritius Papeda", "Leech Lime" or more correctly "Caffre Lime" from which our "Kaffir Lime" is most likely a nineteenth century colonial corruption) has its leaves used in Thai cooking as the basis of many dishes including one of my favourites, Kung Tom Yom or Prawn Soup.