As the temperatures drop, we see the contents of the family fruit bowl change – gone are the soft, succulent summer fruits, first replaced by fragrant autumn beauties, which then give way to their robust, hardy winter cousins. I love eating with the seasons and relish the suitability of each season’s bounty for its climatic counterpart. It’s only logical then, that in the cold, dark (germ-laden) winter, when all we want to do is hibernate, bright zesty citrus is in season – just when we need a potent vitamin C boost and a burst of zippy flavour. Mandarin oranges are the longstanding darling of the school lunchbox, and quite rightly so. Child-sized, conveniently packaged, easy to peel and segment (even for those whose motor skills are still developing) and with a universally-appealing sweetness, what’s not to like?
You’ll be pleased to note that mandarin trees are just as suitably-sized and easy to deal with in the home garden as they are in the kitchen. A small tree, properly cared for, can produce a ridiculous amount of fruit. If your only experience with the humble mandarin orange consists of exposure to the membrane-less segments found in cans imported from faraway lands, do not despair (for I too have an addiction to those strange delicacies – more on this later!). I suggest you find a spot in your garden for a tree, apply a modicum of care and attention, and in no time, you’ll be harvesting your own glowing globes. Throw a handful in your work bag and I guarantee you’ll spend a few mindful moments with a pinch of childhood nostalgia, peeling away the skin, meticulously removing the lace-like pith and methodically separating the segments before enjoying the homegrown sweetness within. On that subject, if you’re not too fussy, eat as much of the spongy white pith as you can – it actually contains calcium and fibre, plus immune-boosting vitamin C and flavonoids. Mandarins are also highly ornamental, with their stunning evergreen foliage a striking contrast to the golden fruit and highly fragrant flowers.
Mandarins: a short family history
The citrus family tree is a complex one – true mandarins are considered to be one of the pure ancestral citrus taxonomic groups, along with the pumelo and the citron – all of our domestic citrus, from grapefruit to lemons and limes are hybrids derived from these three groups. The mandarins (Citrus reticulata, where the species epithet means ‘netted’, a reference to the lacy pith beneath the skin) are small, thin-skinned oranges, having themselves several different classification systems used to sort their members; tangerines and tangelos also belong here and the latter terms are sometimes used interchangeably with mandarin.
Key features which distinguish mandarins from oranges are their small size; sweeter, distinctive flavour; sometimes flattened shape; thin, loose, easily-detached skin and reduced amount of pith present beneath the skin. The term mandarin is actually a loan word translation of the Swedish mandarin apelsin, itself derived from the German Apfelsine, or ‘Chinese apple’. Their initial wild points of origin appear to be Japan, Vietnam and South China, with evidence of two distinct episodes of domestication in southern China’s Nanling Mountains – once in the north and once in the south, from distinct wild subspecies. This has resulted in two distinct genetic clusters, which all domesticated mandarins can be traced back to. The northern cluster has larger size, reddish fruit – to which the modern Satsuma and Kishu types belong to; and the southern group has smaller, yellower fruit to which the modern Willowleaf and Dancy types belong. The very sweet, often seedless Satsuma mandarins are sometimes classified separately as Citrus unshiu.
‘Commercial’ cultivation began in central China around 300 BC, but despite their popularity across Asia, mandarins are thought not to have reached much of the wider world, including the Antipodes, until the 1800s. The Satsuma cultivars are widely popular in Japan (they originated from China and/or Japan, given this plant family’s tangled history I guess we’ll never know where for sure) and the gifting of mandarins at Christmas actually stems from North America, where Japanese immigrants would receive shipments of the fruit from relatives in the New Year period. The tradition was keenly adopted by the locals and merged with the European Christmas stocking tradition. As a result, the eagerly-awaited arrival of the Asian crop, harvested in November and transported across the country on distinctive ‘Orange Trains’ (with the carriages painted orange) signified the start of the holiday season to many.
Mandarins began to be cultivated in North America from the early 1900s, but Japanese-grown imports remained a major source of the fruit, with supply only disrupted by hostilities between the two countries during World War Two.
Suitable climates and growing conditions
Mandarins, like other citrus, are self-fertile, evergreen tropical to subtropicals, and as such will grow well throughout the North Island and the warmer areas of the South Island. They are on the hardier end of the scale, but cold tolerance does vary a bit with cultivar. They will survive and produce, even in colder areas, if the planting site is carefully chosen and there is provision of shelter, especially for young plants. Given most mandarin trees have a small stature, pot culture is a suitable option, as you can shift the plants in and out of a conservatory or greenhouse as the seasons change. If frosts, occasional or otherwise are the problem, consider products such as fabric frost cloth to swaddle your trees with, or wax-like, spray-on ‘liquid frost cloth’ as an intermediate solution. Because mandarin fruit is thinner-skinned than a lot of other citrus, the fruit is more susceptible to cold temperature injury.
It's best to buy nursery-grown grafted mandarin trees, as citrus seeds don’t necessarily grow true to type and seedling plants will take longer to produce fruit. Of course, this shouldn’t discourage you if you have a curious mind, time on your hands and plant breeding aspirations. Going for grafted plants also gives you the option of choosing plants on dwarfing rootstocks if you have space constraints. Some citrus flowers will remain unpollinated but still go on to produce seedless fruit, a process known as parthenocarpy. This can be quite a desirable concept commercially (think seedless grapes and watermelons) and obviously produces fruit popular with picky eaters too!
Conversely, some mandarin cultivars (clementine types in particular) will become overly seedy if planted near polliniser citrus such as grapefruit, tangelos and some other mandarin cultivars such as Encore. It can be hard to allow sufficient separation distance between trees to prevent this in a small home garden, but is worth bearing in mind.
Site selection and planting
Plant mandarins from any time in late autumn to early spring, but avoid midwinter planting in frosty areas. Select a warm (full sun or partial shade), frost-free, sheltered position where the plant will be protected from strong winds and allow at least four metres of space between plants. Mature trees average three to four metres in height, with a similar spread. Windbreak cloth and stakes for protection in the first couple of years can also be beneficial in marginal conditions. They are tolerant of a range of soil types, but a fertile, well-drained, slightly acidic loam soil is ideal for mandarins, although they can crop well in lighter, sandy or clay soils if compost and mulch is applied.
You may have the option of selecting trees grafted onto a particular rootstock suitable for your soil type. A light dressing of fertiliser can be given after planting and mulch around the base of the tree (but kept well away from the trunk) is advantageous. Water well to settle the soil in around the roots.
Culture and care
Mandarins, like other citrus, are quite heavy feeders, requiring several applications of fertiliser throughout the year for reliable crops and to maintain optimum tree health. Several proprietary brands of citrus-specific fertiliser blends are readily available, containing the usual nitrogen, phosphorus and potassium, along with additional sulphur, magnesium and calcium plus trace elements. Start with 1.5 kg annually for young trees, increasing by about half a kilo a year to a maximum of 5 kg per year for a large, mature tree. This should be split into at least two applications, two-thirds applied in late winter and the other third in late summer. Try and apply the fertiliser just before a rain event or water in well after applying. Spread the fertiliser around the base of the tree to the dripline (the zone underneath the outer circumference of a tree’s canopy, where water drips from onto the ground when it rains). Aim for a coverage of about a cupful of fertiliser per square metre of ground.
Irrigation is also of key importance for optimum fruit production, especially for young trees and during the fruit development phase. Mature mandarin trees are moderately drought-tolerant, more so than oranges. Avoid overwatering (which results in increased disease pressure) and waterlogging, which is likely to lead to root rots. To ensure plenty of juicy fruit, keep the water up right throughout summer and autumn, as on-and-off watering can lead to dry, pithy, thick-skinned fruit. Have you been put off planting a mandarin tree because of experiencing dry, pithy homegrown fruit in the past? Citrus fruit doesn’t ripen further once off the tree, so you need to harvest it when it is properly ripe, but leaving mandarins on for too long can actually render them dry and unpalatable too. Held on the tree for too long under wet conditions, they develop ‘puffy’ skin, which is also undesirable.
You can expect your first crop of fruit two to four years after planting (grafted plants) or four to six years (seedlings) – to help young trees establish, it is best to remove most, if not all, of the fruitlets in the first year or two. Some judicious thinning helps avoid biennial bearing in later years, remove small or misshapen fruit and fruit that lacks leaves nearby to help feed it.
In New Zealand, the main harvest period for mandarins is May through October, kicked off by Satsumas, then the Clementines, followed by other varieties such as Burgess Scarlett. There are also much later summer-fruiting varieties with a long fruiting season, such as Encore (ripe October-November to February and can be stored as late as April).
Mandarins generally form their own neat, compact structure and so little in the way of major annual pruning is required. As you harvest any citrus fruit, it is good practise to remove each fruit using secateurs, with a long section of stalk attached (about 5 cm), then cut this off close to the fruit, leaving a nub of stem attached. Removal of this extra wood when picking encourages new fruiting wood to grow. Follow the standard rules for of removing the “three Ds” (dead, damaged and diseased wood) for general maintenance pruning after the main harvest is complete. Evergreen trees store much of their flowering and fruiting resources in the leaves and over-pruning can therefore have a major impact on the next year’s crop.
Pests, diseases and what to do about them
Mandarins, in particular Satsumas, are susceptible to anthracnose, a fungal disease caused by Colletotrichum gloeosporioides. Symptoms include branch dieback, premature leaf drop, visible spore deposits on leaves and twigs, and speckling or scald-like patches on the surface of fruit. Severe infections can be detrimental to fruit that is placed in cold storage.
Citrus scab or verrucosis (Elsinoe fawcettii, syn. Sphaceloma fawcettii) is another fungal disease which causes damage that in terms of fruit production is largely cosmetic, but over time the infection can cause a decline in tree vigour. If your tree is badly affected, you are best to treat it. A copper fungicide spray timed to coincide with when the petals have fallen and fruitlet formation has taken place in late spring or early summer, and again in late autumn or early winter should take care of both of these diseases.
The soil-borne fungus Phytophthora is responsible for a host of issues with citrus – amongst them collar rot and gummosis affecting the trunk and limbs, root rots, and brown rot affecting the fruit. Buying grafted trees on the Phytophthora-resistant Poncirus trifoliata rootstock and planting in a well-drained soil type will help home growers largely avoid these issues.
Maintain a good crop hygiene regime and remove any sources of disease inoculum from the tree as you find them during the growing season and again at pruning time when the main crop has been harvested. Diseased plant material should be collected up and burned or disposed of with your household waste, not composted.
In terms of insect pests, the main culprits are sucking insects (scales, aphids, mealybugs and whitefly), whose feeding activity and exudates cause black sooty mould to develop on fruit and foliage. Sooty mould on fruit is purely cosmetic, and easily scrubbed off with the aid of a nail brush and some warm water. Thrips, leafroller caterpillars and citrus rust mites can also cause detrimental effects – a vegetable or mineral oil-based spray in February and again in May will help to keep these in check, and there are also softer-option combination products such as pyrethrum-and-oil mixtures or neem oil that combine insecticidal compounds with the smothering effect of oils. It is also worthwhile protecting and encouraging beneficial insect populations in your garden – one of our lemon trees harbours a few sap-sucking guests but also a thriving population of Halmus chalybeus, the steelblue ladybird, the larvae and adults of which are voracious predators of the sucking pests previously mentioned. Other generalist beneficial insects and predatory mites can also help keep citrus red mite populations at bay, so bear these in mind when selecting any chemical controls. The guava moth, Coscinoptycha improbana, also known as the fruit driller moth can also be an issue. The insect spends much of its lifecycle inside fruit, with the larvae burrowing in a day after hatching from eggs, largely rendering spray programmes ineffective. With a wide variety of host plants providing year-round breeding conditions in areas like Northland, the home gardener is probably best to resort to netting trees or dare I say it, individually bagging fruit to prevent the adult moths laying eggs on ripening fruit. Practise good crop hygiene by collecting all fallen fruit and either freeze it to kill the insects or feed to livestock – don’t compost it, as this gives the insects a chance to complete their life cycle.
New Zealand has its very own endemic citrus tree foe in the form of Oemona hirta, a longhorn beetle. Otherwise known as the whistling or singing beetle, its penchant for citrus trees as habitat has earned it the moniker of ‘lemon tree borer’. Somewhat of a generalist, the host range of this adaptable beetle now includes a long list of exotic species, as well as the native plants it would have originally existed on. Visible damage to trees may initially be in the form of wilting foliage and/or dieback. Due the larval stage living exclusively inside the tree, the first outward signs of their presence may be exit holes bored to the outside of the trunk, through which powdery frass is excreted. For borer control, there are chemical treatment options available which can be applied through frass exit holes. You can opt to prune judiciously to remove infected branches, avoiding doing this during the egg-laying time period (September to January) as female beetles will happily lay eggs on freshly-cut wood, and painting all cuts with a wound sealant immediately after pruning. Practise good orchard hygiene, removing all dead and diseased plant material from under your trees on a regular basis, as eggs and larvae can survive for some time on excised plant material left on the ground. There are three parasitoid wasps which are natural enemies of the lemon tree borer, so providing a hospitable environment for these beneficials in the form of shelter, nectar, pollen and using ‘softer’ chemical control options will also assist your management strategy.
Varieties: My top picks
Silverhill – early ripening and well-suited to cooler climates. Heavy crops of thick-skinned but easy-peel, low-acid, sweet fruit that is easily segmented.Miho – very early, cold-tolerant. Bears heavy crops of mild-flavoured seedless fruit and being slow-growing, is particularly suited to container culture.
Corsica No. 2 – ripens June-July, fruit are a good size, easy-peel and juicy with a tangy flavour and few seeds.
Encore – a summer-fruiting cultivar producing heavy crops of easy-peel fruit with good flavour. Crop will hang on the tree for an extended period. Low seed count. Vigorous.
Burgess Scarlett – a vigorous variety producing medium-sized fruit with a rich, aromatic flavour. Somewhat prone to biennial bearing.
Thorny – an older variety with, surprise surprise, a few thorns, but outstanding flavour. Small to medium fruit, ripens late winter and stays juicy on the tree. Hardy.
Afourer – a ‘supermarket’ mandarin (commercial variety), better suited to warmer areas. Vivid orange skin, easy-peel and seedless if grown away from sources of cross-pollination. Juicy with a rich flavour. Fruits late winter.
What to do with your crop
Mandarins are best known as a fresh dessert fruit, perfect for eating out of hand as no utensils are necessary for its preparation. It’s hard to compare the commercially-canned segments with the fresh article, although I do really enjoy eating the former – something about the texture and the nondescript, barely even citrusy flavour plus a touch of childhood nostalgia? I used to wonder how the membrane around the segments was removed so perfectly, imagining scores of highly-skilled, nimble-fingered people lining factory tables. Well, the reality is not so romantic. The fruit are first scalded with hot water to loosen the skin, then placed in a lye (sodium hydroxide solution) bath to dissolve the pith and membranes. Finally, they are rinsed well in fresh water and then heat-canned in sugar syrup.
If you have a mandarin glut, you could try substituting mandarins in some of my other citrus recipes – how about mandarin curd or mandarin squash concentrate (see link for curd and squash recipe in YBFB: Beyond the Meyer lemon or curd in YBFB: Passionfruit); or mandarin liqueur (YBFB: Oranges). Mandarins make a nice mild marmalade but it doesn’t set as well as other citrus marmalades – you can add some grapefruit, powdered pectin, a jam-setting mix sachet or jam-setting sugar to help improve the gel.
Mandarins are used in both sweet and savoury recipes in Asian cuisine – sun-dried mandarin peel, known as chen pi in Chinese is used to flavour poultry dishes, desserts and added to tea blends, imparting a slightly sweet, then bitter and pungent flavour. Known by the same name in Japanese, it is an important ingredient in the seasoning blend shichimi tōgarashi (seven-flavour chili pepper).
A bit of a cheat’s recipe, but don’t judge me. Handy when guests are due and all you have on hand is a bunch of store-cupboard staples.
Half a 200 g pack of savoiardi (lady finger) biscuits
¼ cup mandarin marmalade
¼ cup mandarin liqueur
1 packet orange jelly crystals
300 ml boiling water
1 tin mandarin segments
About 500 g prepared, cold custard (I make my own with 500 ml milk, two egg yolks, 2-3 tbsp of custard powder (or 2 tbsp of cornflour and 1 tsp vanilla), and 2 tablespoons sugar)
Make up the jelly with boiling water in a glass jug (note the reduced quantity of water), then drain the mandarin segments and add to the jelly. Refrigerate until barely set. Spread the savoiardi with the marmalade and place in a large serving bowl or dish. Evenly drizzle with the mandarin liqueur.
Top with the barely set jelly/fruit mix and return to the fridge so it firms up. Top with the custard and return to the fridge until ready to serve. Include whipped cream on the side if you’re feeling particularly extravagant.
Anna-Marie Barnes is an active member of the New Zealand Tree Crops Association who endeavours to grow and preserve as much of her own fresh produce as possible. When the weather’s no good for gardening, she can usually be found inside working on a batch of homemade cheese or soap.
The New Zealand Tree Crops Association is a voluntary organisation promoting interest in useful trees, such as those producing fruit, nuts, timber, fuel, wood, stock fodder, bee forage and other productive crops. Find out more about the NZTCA here: https://treecrops.org.nz/
Disclaimer: the information supplied above is of a general nature and provided as reference material only. In regards to pest and disease control, please consult your agrichemical consultant for suitable products, application rates and further region-specific information.
Mandarin tree with fruit x 2 – Anna-Marie Barnes
Mandarin fruit and flowers – Couleur, via Pixabay.com
Mandarin fruit – Steve Buissinne, via Pixabay.com