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

This is a promiscuous group of citrus, that have been interbred from several species and strains and as such contain few true mandarins or mardarines at all, but we'll call them mandarins here. The mandarin clan have long time suffered the dilemma of having some 'seedless' varieties that unfortunately have pretty poor flavour when compared to their 'seeded' cultivars. This has led home gardeners to avoid them somewhat in my region, in favour of other more reliable citrus. The most popular varieties in the supermarket are the commercial cultivars, that have little merit for the home garden, since the keeping characteristics are not so important. The distance from the tree to the kitchen table if you get that far, is seldom a problem to the home gardener.

Commercially grown mandarins and clementines account for only 7 million tonnes of fruit globally, which when compared to the orange crop of about 44 million tonnes, is a drop in the ocean. While oranges mostly grow in Mediterranean climates the mandarin and its close relative, the clementine have a range of varieties that thrive in the tropics as well as in outback areas and the cooler seaboard regions. The clementine cultivars are 'Dancy', 'Honey Murcott', 'Marisol' and 'De Nules', but there are many cross-bred mandarin-clementines too, such as 'Ellendale' and 'Nova'. The clementine seems to have far less seeds than the mandarins and they also have skin that adheres to their flesh more tightly, but apart from that I'll treat them as one and the same.

Now mandarins are quite specific about where they grow best. They thrive when they grow with long daylight and dry cloud-free winters from May through to November, when they set most of their fruit. This gives the inland region of Mundubbera and Gayndah in Queensland a real advantage, which is why some of the sweetest mandarins in the markets come from those regions. Certainly amongst the earlier cultivars anyhow. The later varieties, such as 'Ellendale' that come from the Riverland in South Australia and the Sunraysia in Victoria certainly have more sugar in October through to early December, due to the fact that those areas get far more long sun-drenched days at that time of year, than in Queensland. The ideal soil acidity is in the range of pH 6.0-6.5, but in South Australia 'Ellendale' grows quite well on pH 7.5. On alkaline soils, there are always nutrient deficiencies, where due to the high pH, the phosphates get locked up, as does the available iron and zinc, plus a few minor trace elements. Even in the warm growing areas of Queensland and Western Australia on acid soils, they can suffer from boron deficiency and of course calcium and copper. On acid soils of pH 5.0 in Queensland, dolomite is added at the rate of 100-400 grams per square metre to raise the pH to 6.5. Gypsum is added at the rate of 300 grams per square metre to provide calcium in stable soils, since it does not effect the soil pH. In Western Australia and in South Australia gypsum is used exclusively to improve drainage on clay based soils and to provide calcium if that is needed, but dolomite is seldom used.

The main elements in a fertiliser that mandarins need, are nitrogen, phosphate and potassium, in a fairly balanced ratio. In Queensland they mostly use N:P:K 11:10.5:10, but in South Australia because of the mostly alkaline soils, more phosphate needs to be added because that gets locked up due to the high pH. Some of our most popular enriched organic lifter type fertilisers have an N:P:K of 5:4:5, so that in South Australia and on any other alkaline soils you will need to add extra phosphates in the form of superphosphate. There aren't many 'organic' cures to this conundrum. Peter Young claims that a good Queensland thunderstorm with plenty of Hughie bolts, will deliver 20 kilograms of free nitrogen per hectare, but a short-term nitrogen excess can cause puffiness in the mandarin fruits, so that extra potash needs to be added to keep the nutrient uptake in balance. If that goes right over your head, don't worry about it.

Another nutrient consideration for organic growers is that the enriched organic lifter type fertilisers rely on their boron from the poultry sweepings and of course the chickens relied on the boron in their feed to get that in the first place. Now that's fine if the grain has come from SA or those parts of WA with plenty of boron in their soil, but not so promising if it's come from Queensland or northern NSW, where boron deficient soils are common. Applied as a supplement every 3-4 years, you'll never know you had a problem, but the boron deficiency symptoms are brown segments in the fruit and in really severe cases, brittle yellow new growth. Any areas with a salinity problem in their irrigation water are unlikely to have boron deficiency. Zinc deficiency is common in SA and Qld, but because of the high pH in SA it needs to be applied as a foliar spray during the growth periods. The same applies for magnesium for the same reasons, except that the effect is sun-burnt looking yellow leaves with a triangular green patch at their base. Manganese is available in low pH soils but locks up the iron from about pH 6.5 and lower. Iron is also locked up in high pH soils, causing a yellowing of the leaves, that shows a prominent green vein.

Given that most home gardeners water by micro-irrigation systems these days, it probably goes without saying that the balanced citrus fertilisers sold all over the country, need to be applied evenly under the trees and are best mulched in the hot areas of the country, with the mulch removed during the wet season in both the tropics and the cool areas. A common problem on mandarins and oranges is fruit split. It is true that the 'Washington Navel' orange probably has a genetic weakness in this area, but the others split by drought early in their fruit set period followed by excess water as they mature. The skin development is restricted on the tiny fruit that never recovers as it ages and is basically flawed when we start to notice it.

There are many deficiencies attributed to nutrient lock-up on citrus, but probably the most common cause of poor nutrition in your trees is that the root system is poorly developed due to planting or a high water table of poor drainage, so that the tree does not have a large enough network of roots from which to draw its sustenance. Drainage is critical for the citrus to thrive. If in doubt start with a generous top-dressing of gypsum at 300 grams per square metre. This will open up the soil structure within a few hours and it doesn't need to be dug in, just irrigated.

Most keen gardeners would know that their citrus are grown on the root stocks of other species or selected forms, to provide disease resistance and tolerance to various soil types, that their scion cultivars cannot endure. For this reason it is important to always buy your citrus in your local region. There are also restrictions on the movement between several states, due to the incidence of Citrus Leaf-Minor. The 'Cleopatra' rootstock is a wonderful mandarin rootstock for South Australia as is the 'Rough Lemon' because they tolerate heavy clay soils and an alkaline reaction, but in the warm humid regions disease resistance is more important, so 'Troyer' is used in the eastern states and in Western Australia, because it has considerable resistance to the water moulds, of Phytophthora species. 'Troyer' is a hybrid Poncirus trifoliata X "Sweet Orange" and if it reverts it will soon be detected since the root-stock has very distinctive three lobed deciduous leaves with long thorns on the maturing wood. I often get complaints from gardeners wanting to know what has turned their Mandarins sour. On close examination it's usually the 'Cleopatra' root-stock that has suckered and emerged in the canopy undetected, since it has ordinary Mandarin leaves unlike the distinctive P. trifoliata hybrids. These set fruit and look just like the 'Imperial' scion, but not like the sweet taste of 'Imperial' or 'Emperor'. There is a movement towards dwarf root-stocks, so we can squeeze more trees into smaller yards these days, but although 'Flying Dragon' is being used in California, I haven't seen mandarins offered for sale in Australia on this rootstock, although several nursery folk are trying it for compatibility and fruit set. The Californian experience doesn't always transfer well to Australia, since they grow such different cultivars in different micro-climates.

'Page' is one of the earliest and tastiest of the home grown cultivars. It's very popular in Florida USA and does well in Brisbane and Sydney. It's actually a 'Minneola' tangelo crossed with a clemantine mandarin and looks more like an orange than a mandarin anyhow. You need to plant more than one 'Page' since they are self sterile and need a pollinator. is one of the earliest and tastiest of the home grown cultivars. It's very popular in Florida USA and does well in Brisbane and Sydney. It's actually a 'Minneola' tangelo crossed with a clemantine mandarin and looks more like an orange than a mandarin anyhow. You need to plant more than one 'Page' since they are self sterile and need a pollinator.

'Nova' comes next in the taste stakes as an early variety, with large pale orange fruits and lots of seeds. It's a very vigorous clemantine mandarin, which indicates it is almost seedless, but has thorns, which means it's not that popular in the home garden. It also needs a pollinator. comes next in the taste stakes as an early variety, with large pale orange fruits and lots of seeds. It's a very vigorous clemantine mandarin, which indicates it is almost seedless, but has thorns, which means it's not that popular in the home garden. It also needs a pollinator.

'Imperial' is the most popular commercial cultivar and a home garden favourite originally bred in 1890 at Emu Plains near Sydney. It is an early mandarin with smooth pale skin and a slight neck to the fruit. They can become puffy with age and nitrogen excess. The leaves of the 'Imperial' are quite slender and distinguish it from most other mandarins. is the most popular commercial cultivar and a home garden favourite originally bred in 1890 at Emu Plains near Sydney. It is an early mandarin with smooth pale skin and a slight neck to the fruit. They can become puffy with age and nitrogen excess. The leaves of the 'Imperial' are quite slender and distinguish it from most other mandarins.

'Ellendale" (syn. "Ellendale Beauty") is a mid to late season variety that bears its fruit from July to September in Mundubbera Qld. and in the Riverland SA. When grown on the east coast the fruit frequently splits. The fruits have a very rich flavour with only a few seeds. It is one of those varieties where the fruits become puffy if left on the tree too long.... but what chance is there of that? It is an Australian variety selected from the Ellendale orchard on the banks of the Burrum near Bundaberg Qld. in 1878. It's one of our main export mandarins, because it stores so well. (syn. "Ellendale Beauty") is a mid to late season variety that bears its fruit from July to September in Mundubbera Qld. and in the Riverland SA. When grown on the east coast the fruit frequently splits. The fruits have a very rich flavour with only a few seeds. It is one of those varieties where the fruits become puffy if left on the tree too long.... but what chance is there of that? It is an Australian variety selected from the Ellendale orchard on the banks of the Burrum near Bundaberg Qld. in 1878. It's one of our main export mandarins, because it stores so well.

'Ellenor' is a fairly new variety that is proving to be a productive cultivar on a tree with very few thorns that produces a very tasty rich juicy although fairly small fruit. It's mid season fruits are a rich reddish orange. The tree needs a good deal more fertilising than most other citrus or deficiencies will occur and fruit set will be low. With this treatment the fruit set can be so large that it may even need thinning to get quality sized fruit. is a fairly new variety that is proving to be a productive cultivar on a tree with very few thorns that produces a very tasty rich juicy although fairly small fruit. It's mid season fruits are a rich reddish orange. The tree needs a good deal more fertilising than most other citrus or deficiencies will occur and fruit set will be low. With this treatment the fruit set can be so large that it may even need thinning to get quality sized fruit.

'Emperor' is a mid season, virtually thornless mandarin variety with a bright orange coloured skin on a flat fruit, that rates behind 'Imperial' and 'Ellendale' in my taste test. Its prolific fruit has numerous seeds and becomes puffy when left on the tree too long. Them fruit needs to be clipped or it will pull the top from the fruit, which doesn't matter if you're eating them fresh from the tree, but they will deteriorate in storage. It grows well in the eastern coastal regions and is a very popular home garden variety. 'Emperor' appears to have been selected from a batch of chance seedlings grown on from stocks originally imported from China. is a mid season, virtually thornless mandarin variety with a bright orange coloured skin on a flat fruit, that rates behind 'Imperial' and 'Ellendale' in my taste test. Its prolific fruit has numerous seeds and becomes puffy when left on the tree too long. Them fruit needs to be clipped or it will pull the top from the fruit, which doesn't matter if you're eating them fresh from the tree, but they will deteriorate in storage. It grows well in the eastern coastal regions and is a very popular home garden variety. 'Emperor' appears to have been selected from a batch of chance seedlings grown on from stocks originally imported from China.

'Tropical Mandarin' grown in Darwin is probably a selection of 'Emperor' that has been grown in the top end for over 30 years and is now in commercial production at Bees Creek NT and Humpty Doo NT. It peels easily, has an excellent juicy flavour in its main season from April to July in the north. The skin colour has a green flush and seldom colours up in the way that 'Emperor' does in areas with a cool night. grown in Darwin is probably a selection of 'Emperor' that has been grown in the top end for over 30 years and is now in commercial production at Bees Creek NT and Humpty Doo NT. It peels easily, has an excellent juicy flavour in its main season from April to July in the north. The skin colour has a green flush and seldom colours up in the way that 'Emperor' does in areas with a cool night.

'Glen Retreat' (syn. 'Beauty') is a popular mid season mandarin that is a prolific bearer with virtually no thorns. It has fairly large bright orange juicy fruit with lots of seeds and a pleasant flavour. It goes puffy if left on the tree past its maturity. The fruit has a high neck and needs to be clipped from the tree rather than picked, to keep the skin in tact. (syn. 'Beauty') is a popular mid season mandarin that is a prolific bearer with virtually no thorns. It has fairly large bright orange juicy fruit with lots of seeds and a pleasant flavour. It goes puffy if left on the tree past its maturity. The fruit has a high neck and needs to be clipped from the tree rather than picked, to keep the skin in tact.

'Fremont' and frequently written as 'Freemont', is a really wild tasting early mandarin with a brilliant reddish-orange fruit. I've seen this variety growing near Mersin in southern Turkey and it deserves to be more widely grown in Australia too. and frequently written as 'Freemont', is a really wild tasting early mandarin with a brilliant reddish-orange fruit. I've seen this variety growing near Mersin in southern Turkey and it deserves to be more widely grown in Australia too.

'Hickson' is a popular mid season mandarin variety for home gardeners, well suited to the warm coastal areas where high humidity prevents 'Ellendale' from thriving. A large and spreading tree that tends to bear well in alternate years. is a popular mid season mandarin variety for home gardeners, well suited to the warm coastal areas where high humidity prevents 'Ellendale' from thriving. A large and spreading tree that tends to bear well in alternate years.

'Kara' is a seedy little mandarin, but with a fresh wild taste that's popular in Perth home gardens. It was bred by H.B. Frost in California in 1915, but not released until 1935 from a cross between the 'Owari satsuma', which is a Japanese mandarin and the cultivar 'King of Siam' which is a "King Mandarin", Citrus nobilis. The fruit is easily peeled but some complain of its acidity. It is however an important mandarin for picking in September and October, when so many of the early and mid season mandarins have finished or their fruit is of such poor quality. is a seedy little mandarin, but with a fresh wild taste that's popular in Perth home gardens. It was bred by H.B. Frost in California in 1915, but not released until 1935 from a cross between the 'Owari satsuma', which is a Japanese mandarin and the cultivar 'King of Siam' which is a "King Mandarin", Citrus nobilis. The fruit is easily peeled but some complain of its acidity. It is however an important mandarin for picking in September and October, when so many of the early and mid season mandarins have finished or their fruit is of such poor quality.

'Minneola' tangelo (syn. 'Honeybell') has a mid to late season crop on a fairly large tree with conspicuous deep green leaves. It's a cross between the 'Duncan' grapefruit and the 'Dancy' mandarin. The large red-orange fruits have a distinctive neck and a rich tart flavour, juicy and aromatic when warmed up in cupped hands. They are probably the most frost tolerant of the citrus. I've seen them growing at Quorn SA where -4_C frosts are common. tangelo (syn. 'Honeybell') has a mid to late season crop on a fairly large tree with conspicuous deep green leaves. It's a cross between the 'Duncan' grapefruit and the 'Dancy' mandarin. The large red-orange fruits have a distinctive neck and a rich tart flavour, juicy and aromatic when warmed up in cupped hands. They are probably the most frost tolerant of the citrus. I've seen them growing at Quorn SA where -4_C frosts are common.

'Honey Murcott' or 'Murcott' tangor is a late bearing hybrid mandarin x tangerine. The tree develops long weeping branches, that are almost thornless. The fruit is bright orange with a tight skin and very juicy. It grows well in South Australia's inland areas where its delicious sweet fruit sets from October to December. Inland Queensland it matures August to September. While it is a heavy setter of fruit they tend to have alternate years of light crops. or 'Murcott' tangor is a late bearing hybrid mandarin x tangerine. The tree develops long weeping branches, that are almost thornless. The fruit is bright orange with a tight skin and very juicy. It grows well in South Australia's inland areas where its delicious sweet fruit sets from October to December. Inland Queensland it matures August to September. While it is a heavy setter of fruit they tend to have alternate years of light crops.

'Wilking' tangor is the result of a 1925 cross between the "Mediterranean" or "Willow-leaf Orange" and the "King Mandarin", released in California in 1935. It has a compact bushy habit with willow like leaves. The fruit is orange in colour and has an excellent juicy flavour, but with lots of seeds. The fruits do go puffy if left on the tree too long and it tends to crop heavily in alternate years. tangor is the result of a 1925 cross between the "Mediterranean" or "Willow-leaf Orange" and the "King Mandarin", released in California in 1935. It has a compact bushy habit with willow like leaves. The fruit is orange in colour and has an excellent juicy flavour, but with lots of seeds. The fruits do go puffy if left on the tree too long and it tends to crop heavily in alternate years.

The seedless mandarins are mostly clementines, if that makes any sense to you at all!. These modern cultivars have very few seeds and are also not generally as rich in flavour as the mandarins, tangelos and tangors.

'Marisol' clementine matures 3-4 weeks before 'Imperial' and two weeks earlier than 'Oroval'. The fruit is roundish and very soft, so it deteriorates rapidly if not eaten as it ripens. In common with all the clementines they are pretty sensitive to nitrogen excess, which causes a puffiness in their fruits, that also makes their flesh rather bland if overfed. It's a popular variety in Perth. clementine matures 3-4 weeks before 'Imperial' and two weeks earlier than 'Oroval'. The fruit is roundish and very soft, so it deteriorates rapidly if not eaten as it ripens. In common with all the clementines they are pretty sensitive to nitrogen excess, which causes a puffiness in their fruits, that also makes their flesh rather bland if overfed. It's a popular variety in Perth.

'De Nules' clementine also matures at the same time as 'Marisol'. It's a big tree and sets lots of tasty fruit. clementine also matures at the same time as 'Marisol'. It's a big tree and sets lots of tasty fruit.

'Fina' clementine is a popular Spanish clementine, with a strong fragrance, that is not reflected in the taste of its fruit. Well certainly not in the ones I've tasted. clementine is a popular Spanish clementine, with a strong fragrance, that is not reflected in the taste of its fruit. Well certainly not in the ones I've tasted.

'Oroval' clementine is the best tasting of the seedless clementines to my taste-buds and matures after 'Imperial' but still fairly early. clementine is the best tasting of the seedless clementines to my taste-buds and matures after 'Imperial' but still fairly early.

My pick in the best flavour stakes, would be 'Fremont', followed by 'Page', 'Imperial' and 'Honey Murcott'. The 'Emperor' is outstanding providing it is picked with half colour. The longer it stays on the tree it colours up, but the sugar levels drop. 'Ellendale' on the other hand stores well in the crisper for 4-5 weeks and actually has its acidity diminish with storage, which is why it's so popular in the Asian market.