cluster of grapefruit growing on tree

A grapefruit is just a lemon that saw an opportunity and took advantage of it.

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-Oscar Wilde

All hail the greatest breakfast fruit in all its juicy glory. The citrus season is upon us, and what better time to celebrate the reliable citrus heavyweight which tends to live life out of the limelight, the grapefruit. Often tucked away in a quiet corner of the Kiwi quarter-acre paradise, the aptly named Citrus paradisi is the unsung hero of the citrus world. Whether juiced; halved, sprinkled with sugar and grilled; or turned into a sticky but fragrant marmalade, the unique bitter-tart jolt of flavour the grapefruit offers is the perfect morning wake-up. When Tip Top discontinued the grapefruit and lemon Fruju ice block, there was an uproar. Testament to our national adoration for this fruit, we even have our own New Zealand ‘grapefruit’, also known as the Poorman orange or Goldfruit.

A pair of grapefruit spoons reside in the cutlery drawer of our family home, inherited from citrus-loving grandparents. The spoons have a serrated edge on one side, perfect for detaching segments at the breakfast table. Not only does this noble fruit have its own special spoons, but there are also grapefruit knives with a curved blade and serrated tip, designed to ‘hug the curves’ of the fruit during preparation. In the UK it is illegal to sell knives to persons under 18 under the Criminal Justice Act 1988. In 2009, a company sold one of said grapefruit knives to a test purchaser under 16. It was later proven in court that the object was a ‘gadget’ and not a knife, resulting in the court case being thrown out.

Our small home orchard once boasted a healthy grapefruit tree, but it sadly upped and died, seemingly overnight. I suspect a root rot such as Phytophthora was the culprit causing its demise. The only caveat with grapefruit is that the fruit contains several compounds that can cause potentially dangerous interactions with many common medications – you may have seen a little sticker on the box from your pharmacy, advising you to avoid grapefruit and its juice. Heed these warnings at all costs, and perhaps look within the citrus family for a more benign option for your vitamin C fix. For those who can enjoy, unlock your cutlery drawer and prepare for bucketloads of fruit from an attractive, easy-care tree.

Grapefruit: a short family history

Like many other citrus fruits, the grapefruit has a somewhat muddled history. Originating in the West Indies, the fruit we know today is likely a natural hybrid between two parents of Asian origin: the Jamaican sweet orange (a Citrus sinensis variant); and the large-fruited Indonesian pummelo (Citrus maxima). Pummelo seeds were apparently brought to Barbados by a Captain Shaddock in the 17th century, with the fruit not unsurprisingly known as the shaddock. Hybridisation between the two species most likely took place in the ensuing years. In 1814, the naturalist John Lunan used the term grapefruit to describe one form of the hybrid fruit, supposedly because the flavour was similar to actual grapes. Then later, in 1824, the French botanist Chevalier de Tussac noted the cluster-like arrangement of the fruit on the tree and also assigned the name grapefruit, from the French word for cluster, grappe.

What of the grapefruit’s history in Aotearoa? The colony of New Zealand was initially governed via New South Wales; hence the provenance of New Zealand’s citrus stock is most probably Australia. The earliest mention I can find relates to a Poorman orange tree (bearing the fruit now known as the New Zealand grapefruit) producing fruit on Kawau Island in 1856, brought to New Zealand by Governor George Grey. Not a true grapefruit, it is thought to be a pumelo/tangelo or pumelo/ mandarin hybrid (C. maxima x C. reticulata) and is perfectly suited to our cooler climes. Governor Grey passed this variety on to grower John Morrison in Warkworth, north of Auckland, who later selected the well-known clone ‘Morrison’s Seedless’. The name ‘Goldfruit’ was coined in the 1980s as a marketing ploy for export New Zealand grapefruit.

Suitable climates and growing conditions

Grapefruit are subtropical, tending towards tropical evergreen trees and C. maxima x C. reticulata cultivars will generally grow well throughout the North Island and upper South Island. Red-fleshed true grapefruit cultivars may not attain the strong flesh colour that develops in warmer climates, but they and their yellow-skinned kin are worth a try in Northland, where subtropicals tend to thrive. With particular attention to site selection and the provision of some shelter, for example planting under the eaves of your house, the hardier types may crop satisfactorily further south. Exposed coastal conditions are best avoided. If it is particularly windy or just generally cold where you live, you could invest in some sort of protective structure with shadecloth, or be particularly vigilant with fabric frost cloth. There is also a wax-like spray-on ‘liquid frost cloth’ you can use as an intermediate solution. Grapefruit tend to form larger trees at maturity than some other citrus, so container-grown trees (shifted inside during winter) might be pushing the limits, but are worth a try. You might, however, be lucky enough to find a grapefruit tree on dwarfing rootstock, which would be ideal for this purpose.

Grapefruit are self-fertile, so you only need one tree in the garden to produce fruit. The flowers are produced in spring and summer and are pollinated by insects. The fruit matures six to eight months after fruit set. An established, healthy tree can produce in excess of 25 kg of fruit in a season. Like other citrus, the fruit holds well on the tree. Grapefruit don’t ripen further once harvested, so don’t pick them early unless you need immature fruit for making marmalade.

As with most citrus, growing from seed is a lengthy and haphazard process. You can propagate at home via budding into seedling rootstock, but again, the effort and outlay on materials (e.g., specific rootstocks) is not really worth the trouble unless you have a special interest in citrus propagation. Seedlings will take three to five years to produce a crop, while if you choose a healthy, grafted plant of a named cultivar, the wait for fruit reduces to just two to three years. To help the tree establish, it is best to remove most, if not all, of the fruitlets in the first year or two.

Site selection and planting

Plant grapefruit trees any time from late autumn to early spring, but avoid midwinter planting in frosty areas. Select a warm, frost-free, sheltered position where the plant will be protected from strong winds and allow six to eight metres of space between plants. Mature trees are quite large, reaching about four to six metres in height. Windbreak cloth and stakes for protection in the first couple of years can also be beneficial in marginal conditions. A fertile, well-drained, slightly acidic loam soil is ideal for grapefruit, although they can crop well in lighter, sandy or clay soils if compost and mulch is applied. A light dressing of general 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. If you wish to have seedless fruit (easier said than done…), plant well away from any other citrus trees!

Culture and care

Grapefruit require 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 two or three applications, two-thirds applied in late winter and the other third in late summer. An alternative regime could see you break the total quantity down into six-weekly applications from early spring to 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, as citrus are not drought-tolerant, although a balance must be struck to 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 spring and summer, tapering off again towards mid-late autumn. On-and-off watering can lead to dry, pithy, thick-skinned fruit.

Pruning

Citrus trees generally form their own neat structure and so little in the way of major annual pruning is required. Light pruning in the formative years to produce a neat shape is beneficial, as is keeping the lower branches clear of the ground. 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. Some grapefruit cultivars are more vigorous than others, and will need some extra branches removed to keep an open canopy. As you harvest the 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.

Pests, diseases and what to do about them

Verrucosis (citrus scab) is a fungal disease affecting grapefruit, and while in terms of fruit production the damage is largely cosmetic, over time the infection can cause a decline in tree vigour, so if your grapefruit tree is badly affected, you are best to treat it. Brown rot, another fungal disease, can cause significant fruit loss, and its spores will overwinter in mummified fruit and in cankers on branches, so establish a good crop hygiene regime and remove these sources of 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. A copper spray (e.g., Yates Liquid Copper, applied according to label directions) 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.

In terms of insect pests, grapefruit trees are commonly affected by leafroller caterpillars, mealybugs, various scale insects and thrips. An application of summer oil in February and again in May can assist with scale insects, while Yates Nature’s Way® Citrus, Ornamental and Vegie spray is an organic pyrethrum and oil combination spray that can be applied to combat thrips, mealybugs and leafrollers. Follow the label directions.

If you notice black sooty deposits on your grapefruit tree’s leaves or fruit, you likely have an infestation of scale insects. Yates Conqueror Oil applied at label rates during February and again in May should take care of these as well as other sucking insects like mealybugs, and also mites. Any sooty mould fungus that develops on fruit as a result of feeding by sucking insects is purely ornamental – just scrub the fruit with a nail brush and some soapy water after harvesting.

The New Zealand endemic lemon tree borer beetle (Oemona hirta) may also take a fancy to grapefruit trees, so make sure you conduct any pruning outside of egg-laying season (roughly September to January) and seal any pruning cuts immediately with pruning paint. See Your Backyard Fruit Bowl: Beyond the Meyer Lemon for more detailed information about the lemon tree borer.

Varieties: My top picks

Wheeny (Wheeney) – an Australian C. maxima x C. reticulata selection bearing heavy crops of pale lemon-coloured fruit with a tart lemon-esque flavour. Suitable for cooler areas; cold tolerant once established. Ripens November to March; prone to biennial bearing.

Morrison’s Seedless – the original New Zealand C. maxima x C. reticulata selection, giving rise to the later selections Golden Special and Cutler’s Red (below). Hardy, ripens June to October. Does unfortunately produce seeds if planted near other citrus.

Golden Special – Improved New Zealand C. maxima x C. reticulata selection, the dominant commercial cultivar since 1980. Fruit has few seeds if planted away from other citrus. Fruit is juicy, sweet and tangy. Forms a large, vigorous tree. Fruit ripens September-November but holds well on tree into summer.

Cutler’s Red – New Zealand C. maxima x C. reticulata selection, from Kerikeri in the 1970s. Red-orange skin, quite ornamental because of this. The fruit ripens October-December and its flesh is sweet-tart. Seedy if planted near other citrus.

Star Ruby – a red-fleshed C. paradisi cultivar (orange/pummelo hybrid) well suited to warmer climates (red pigmented flesh may not develop in cooler climates). Mid-late season.

What to do with your crop

Have you tried the much-touted ‘Grapefruit diet’ (also known as the Hollywood or 18-Day diet)? Nope, me neither! I can think of many far more appealing ways to consume this juiciest of fruits. When I think grapefruit, I think marmalade, and my favourite recipe so far is Nadia Lim’s brightly-spiced version – find the recipe here: https://nadialim.com/grapefruit-marmalade-with-cardamom-turmeric-and-ginger/

You might have seen grapefruit seed extract listed as an ingredient in various cosmetic products – the seeds contain antibacterial and antifungal compounds which act as preservatives, as well as being utilised as antiseptics and disinfectants. The essential oil is also widely used in cosmetics, cleaning products and perfumery.

It goes without saying that the fruit makes excellent juices and cordials – see Your Backyard Fruit Bowl: Beyond the Meyer Lemon for my family’s recipe (just substitute grapefruit for lemons – you may need to adjust the amount of sugar to taste). Why not try grapefruit curd as well? You can find the recipe in Your Backyard Fruit Bowl: Oranges.

I’ll leave you with my recipe for grapefruit sorbet – perfect to make now and store for the summer months.

Grapefruit & bitters sorbet

Make some simple syrup by simmering 1 cup granulated sugar and 1 ½ cups water together in a saucepan for 15-20 minutes. Cool and set aside.

Combine 2 cups strained fresh grapefruit juice (pink, white or a mixture) in a bowl with 1 cup simple syrup and add a few dashes of Angostura bitters, to taste. You could include some finely grated grapefruit rind for extra flavour and visual effect. The unchurned mixture might taste quite strong, but remember flavours become muted once frozen.

Whip two egg whites to stiff peaks in a separate bowl, as if you were making a meringue. If you have an ice cream machine, pour the juice/syrup/bitters mixture into the machine’s bowl and churn until almost set. Fold in the beaten egg whites and churn for a further five minutes or until firm.

If you don’t have an ice cream machine, pour the mixture into a couple of two litre ice cream containers, freeze for two hours, remove and beat each portion with a whisk or hand beater to break up the ice crystals. Return to the freezer and repeat the process every half hour to hour until the desired texture is reached. Mix in the egg whites at the last beating. You could also use a food processor for this method. Pack into a freezer-proof container and freeze until ready to use. Remove from the freezer 10-15 minutes before serving for ease of scooping.

If you don’t like consuming raw egg whites, leave them out and instead add a tablespoon of your favourite liqueur to help keep the sorbet’s texture from being too icy. You could also make an Italian meringue, where the egg whites are beaten with hot sugar syrup, and use that as the hot syrup process soft-cooks the egg whites.


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.

Image credits
Grapefruit including cut fruit - Engin Akyurt via pixabay.com
Grapefruit on tree - Dan Ivanov via pixabay.com
Grapefruit juice - nastasyaday via pixabay.com