Your Backyard Fruit Bowl – Coffee

Coffee germination: Roger Burger - Own work, CC0 via Wikimedia Commons

Coffee is the best thing in life because it brings people together.
- Unknown

Harvests are slim in the depths of winter, which for many gardeners is a time of rest, reflection and renovation, and getting lost in the depths of seed catalogues while sitting by the fire. In the next few months, I’ve decided to turn my attention to some edible fruiting crops that can be cultivated from the confines of your house – some slightly more tender, temperature-sensitive crops that have novelty value, but in these times of changing global conditions (climate-related and otherwise) might be quite prudent to have up your sleeve.

I’ve decided to start with everyone’s early-morning darling, coffee. With rising pressure on commodity crops due to tenacious pests and diseases, increasingly warmer temperatures and rising global demand, we are experiencing rapid rises in the price of our favourite imported luxuries – cocoa and coffee amongst the most obvious. While it’s probably not cost effective or remotely worthwhile ploughing up your back lawn for a coffee plantation, committed coffee fiends might find it fun to experiment with a plant or two in a tub in a conservatory or greenhouse. If you’re lucky enough to live in Northland, you can even have a go at growing outside.

While not a regular coffee drinker myself (I like it, but it doesn’t like me), I can definitely see the appeal of growing your own brew. In subtropical climates, the trees can be grown outside and with their glossy evergreen foliage and sweetly-scented flowers, could also be suitable as a small specimen tree for landscaping. If you’re in a cooler climate and looking for an attractive houseplant with a point of difference that’s likely to make it a great conversation starter, look no further.

Coffee: a short family history

Coffee plants (genus Coffea) belong to the Rubiaceae, commonly known as the madder, bedstraw or coffee family. Their better-known relatives include the genera Cinchona, species of which produce the bitter-tasting alkaloid quinine (a famous antimalarial compound, which most of us are more infamously acquainted with as a key element of tonic water, consumed widely with gin), the highly-fragrant ornamental tropical genus Gardenia, and our own New Zealand native Coprosma species. It’s interesting to note this relationship and that settlers here in the 1870s did try to produce a passable beverage from Coprosma fruit. However, Coprosma seeds (which do resemble minute coffee beans) are an awful lot smaller than Coffea seeds and this probably didn’t help an awful lot with early attempts at commercialisation. Heaven forbid, if we should ever be cut off from the rest of the world, Kiwi caffeine fiends might be able to find relief in a local brew harvested from the back blocks, with an ounce or two of patience thrown in for good measure.

Coffee plants are small, shrubby trees native to tropical and southern Africa (notably Ethiopia), and southern Asia. There are well over 100 species in the genus Coffea, but only two have commercial significance and account for most of the world’s commercial production. They are the well-known Coffea arabica (mostly commonly referred to as just ‘Arabica’), which accounts for about 70-75% of the world’s coffee production. It grows naturally at altitudes between 900 – 2,000 m and prefers an average temperature range of 20-25°C. It produces beans which when roasted have a sweet-sharp, full bodied-flavour but a lower caffeine content than other species. The plants are more delicate and have lower yields than Coffea canephora, which is otherwise known as Coffea robusta, or simply ‘Robusta’. C. canephora is a larger, generally hardier tree and accounts for the remaining 25% of global production. It naturally grows at lower altitudes (200 – 300 m) and requires slightly higher average temperatures, 24-26°C. It has higher yields and the beans contain about double the amount of caffeine than Arabica beans. The resultant coffee made from these beans is stronger, but has a harsher, less-refined flavour than that made from Arabica beans. No surprises that for these reasons, it’s the poster child of the instant coffee industry. A third, much less-known species makes a up a tiny proportion (about 1% of global supply), and that is Coffea liberica from West Africa. A large leaved, large-fruited species, it is hardy, and tolerant of droughts and a wide range of soil conditions. If produces fruit with a caffeine content between that of C. arabica and C. robusta, but tends to have a harsh, less-approachable flavour.

Suitable climates and growing conditions

Coffee flowers: Marcelo Corrêa - Own work, CC BY-SA 3.0 via Wikimedia Commons

The global ‘Coffee Belt’ or commercial cultivation zone centres on the equator and extends north to Mexico, the north of India, across to Indonesia and Papua New Guinea, through central Africa and down to the very south of Brazil, encompassing North, South and Central America, the Caribbean, Africa, the Middle East and Asia. New Zealand is obviously well outside this zone, but there are pockets in Northland with a maritime climate in combination with subtropical temperatures where outside production is possible and we do actually have at least one commercial grower!

Ideal conditions for outside cultivation of coffee are those typical of cool to warm, humid tropical climates. C. arabica thrives in a temperature range of 18-21°C and can tolerate mean annual temperatures of up to 24°C. The warming global climate poses a severe risk to coffee production, with increasing temperatures contributing to accelerated fruit development and ripening, which can actually contribute to a decline in the quality of the beans produced. Exposure to temperatures above 30°C can cause physiological deterioration including stunted growth, yellowing of leaves and the development of stem tumours.

Coffee plants are not tolerant of frosts, and while the odd cold night probably won’t hurt, foliage will be damaged at 0°C and plants will likely curl up their toes in anything below -2°C. In areas with warm temperate conditions, they can survive colder conditions with sufficient protection.

In their natural environment, coffee plants can reach 10-12 metres in height, but under cultivation are usually kept to between two and five metres for ease of harvesting, and outdoors in the New Zealand climate plants average around the two-metre mark anyway. Allow two to four metres between plants for block plantings where you plan to prune to size, but if you’re going for a showcase specimen planting of just a few plants, give them a bit more space. Given the right care and conditions, plants are long-lived, around 30-40 years or more.

Plants flower in spring, producing delicate but showy five-petalled flowers with a heady, jasmine-like scent. C. arabica is self-fertile with bisexual flowers, so will produce fruit with just one plant, although cross pollination from neighbours will improve fruit set, yield and the quality of the beans. Pollination is by insects and can therefore experience significant disruption in windy conditions. Coffee beans are in fact the seed of the red coffee fruit, which is known as a ‘cherry’. Two seeds per fruit is the norm, but a small percentage of cherries in each harvest contain just one fruit, known as a ‘peaberry’. Unfortunately, given the challenges of the New Zealand climate, fruit set does not always equate to guaranteed seed (bean) production. In our climate, harvesting of coffee cherries kicks off in December and continues throughout January.

Seedling coffee plants will produce their first fruit at around two to four years of age, with reasonable yields after five to six years and full production at seven to eight years of age. Expect around two kilograms of C. arabica coffee cherries per plant at maturity, which will yield around 400 grams of processed coffee beans – this is a high by-product crop and the unprocessed fresh fruit weight doesn’t directly translate to final yield (more about this later).

Although it is possible to propagate coffee plants from cuttings (and cutting grown plants tend to fruit a little earlier than their seedling-grown counterparts), they grow readily from seed and fresh is best. If you know someone with a coffee plant and can obtain some fresh cherries, pop them in water, discard the ones that float and extract the seeds from the viable ones that sink. Wash the pulp off the seeds, and soak in water for 24 hours. Sow in a tray of seed raising mix at a depth of about a centimetre. Keep warm, moist and in a shady position. Once the seeds germinate, they are known as ‘soldiers’ and look quite comical, a green lollipop stick with a coffee bean sitting on top. The bean then bursts open to reveal the first leaves. Transplant to larger pots as necessary and grow under cover with protection until the plants are at least 50 cm tall.

Site selection and planting

Ripening coffee cherries: Image by Daniel Ramireza via pixabay.com

Care needs to be taken when choosing a spot for your coffee plants. Choose a warm location with both shelter and shade. You may need to consider installing some form of windbreak as coffee plants don’t tolerate wind, salt spray or strong, direct sunlight. Those growing in a permaculture system might like to consider planting coffee as an understorey for legumes such as inga bean, to harness the potential of the legume’s nitrogen fixing capability to in turn provide for the heavy nitrogen demands of the coffee plant. The larger inga bean can also provide much-needed shade, assist with mineralisation of organic matter in the soil and buffer temperature and humidity. Planting on a slope is recommended, which will assist with directing the flow of cold air away from your plants and also help with drainage. Altitude has a pronounced influence on coffee production, which you can read more about here.

In regards to soil type, avoid heavy, compacted clay types, but you may get away with a clay loam. The coffee plant’s general preference is for slightly acid soil (pH 5-6), which clay types won’t necessarily offer. Sandy soils offer good aeration and drainage, but the plants need constant moisture so they may be too free draining.

Incorporating organic matter may help increase the water holding capacity if this is your only choice. Volcanic soil types with good levels of organic matter also get the tick.

Pot culture – the best option for everyone in Aotearoa, outside Northland.

Coffee plants are shallow rooting and hence a good choice for growing in containers. Choose a large pot and a potting mix on the acidic side of the pH scale – you could try Daltons Acid Mix, which is formulated for other acid-lovers such as camellias, azaleas and rhododendrons. Coffee plants are naturally a lower-level species in the forest canopy, so like a bit of shade. Situate out of direct sunlight in your conservatory, greenhouse or tunnelhouse and pay careful attention to watering and fertilisation.

Culture and care

Green coffee cherries: Image by Justin Fishera via pixabay.com

Coffee plants can be planted out from late spring through summer. They are heavy feeders in terms of nitrogen, so consider an application of composted manure and/or blood and bone at planting, and supplement this with regular applications of a balanced general fertiliser year-round.

The plants are not drought-tolerant and require constant levels of irrigation year-round. Be careful to ensure container-grown plants are not allowed to dry out.

Pruning

Prune coffee plants in late winter to early spring. Commercially, coffee plants are trained to have a basic structure of vertical leaders, each with a number of horizontal branches coming off them. Renewal of these verticals takes place about every four years, removing older material while keeping in mind which new verticals need to be encouraged as replacements. In terms of height, keeping plants to around two metres will keep the harvesting process manageable.

Coffee plants can also be coppiced (cut off at ground level) and allowed to regenerate from the stump every four years or so.

Not sure what to plant next? Our backyard orchard advice covers apples, citrus, stonefruit and more.

Pests, diseases and what to do about them

New Zealand’s isolated location and strict biosecurity measures mean the pest and disease issues that affect overseas crops haven’t made it here. Rabbits can be an issue as they have a tendency to ringbark outdoor plants.

Availability

Coffee plants are readily available in New Zealand. You can purchase Incredible Edibles C. arabica plants from Bunnings and Mitre 10. They are also available to home gardeners direct from Ikarus Coffee in Northland and also pop up frequently on TradeMe.

How many plants are you going to need to feed a coffee habit of one cup a day?! I’ve heard 30 plants is a reasonable estimate for this!

What to do with your crop

Green coffee beans:  Image by Jose Luis C.R. via pixabay.com

Coffee cherries will drop from the plant once ripe, but are most commonly hand harvested before this happens and are selectively picked for uniform ripeness.

Once you have a bucketful of bright red cherries, what to do? This is not a process for the impatient, so don’t expect to be sipping a cup of homegrown coffee the following morning.

Soak your cherries in a bucket of water overnight so the beans are easy to extract the next day.

Pop the beans out of the red pulp using your fingers. This will result in a pile of slippery, gummy white beans.

Ferment the slimy layer away – do this by putting the beans back in a bucket of water for a day or two longer until this layer is broken down.

Rinse clean, and dry the beans on absorbent paper in a sunny spot until completely dry – use the bite test to confirm moisture levels. Test a bean by biting it, if it’s still soft and chewy it needs a bit longer.

Once the beans are hard and dry, you need to remove the next layer which is thin and papery and known as the parchment. This can be done with your fingers, which is time-consuming, or Incredible Edibles recommends popping them in your food processor equipped with the plastic blade attachment and giving them a whirl to loosen this layer.

At this stage the beans are ready to roast, but you can also stop now and store the beans for roasting later (apparently green, unroasted beans will keep for up to three years in a sealed container).

To roast, get out your cast iron frying pan, pop it on the stove to heat and set your extractor fan to high.

Once the pan is smoking hot, pop your beans in and keep them on the move. Watch them change colour, and enjoy the crackly soundtrack.

Remove the beans once they reach your preferred level of roast: the darker they go, the stronger the flavour.

Cool the beans down and remove the fine, membrane-like layer of silverskin that will now be detaching from the beans. A clean, dry tea towel, as you’d use when taking the skins off roasted nuts will help here.

Your roasted beans are now ready to grind and brew!

What to do with the leftover cherry pulp? You may just want to compost it, but this leftover pulp can be dried in a dehydrator and used to make cascara, a coffee cherry infusion that is said to have flavours of tamarind, rosehip and hibiscus.

Green coffee leaves can also be harvested, dried, and gently toasted before being brewed with hot water to make an amber-green infusion. It’s said to have a flavour somewhat like green tea.

Not a coffee bean fan? The red flesh of coffee cherries is said to be delicious when ripe, with a pleasing honeydew melon-like sweetness plus a hit of refreshing acidity. The cherries themselves are not that juicy, but the juice can be extracted more easily once the flesh is separated from the beans and makes a pleasant drink.

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.

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/

Image Credits:

Coffee flowers: Marcelo Corrêa - Own work, CC BY-SA 3.0 via Wikimedia Commons
Coffee germination: Roger Burger - Own work, CC0 via Wikimedia Commons
Green coffee beans:  Image by Jose Luis C.R. via pixabay.com
Green coffee cherries: Image by Justin Fishera via pixabay.com
Ripening coffee cherries: Image by Daniel Ramireza via pixabay.com