Arabica
A time-lapse: days, months and years pass in seconds. The clock at the top left counts from the day the seed went into the sand.
Seed to Swan
Grow a coffee tree from a seed: the root, the “soldier”, the butterfly, the nursery, the branches, three days of flowers and nine months of cherries. Then compare arabica, robusta and liberica, and see which variety gives which tree, bean and cup.
A time-lapse: days, months and years pass in seconds. The clock at the top left counts from the day the seed went into the sand.
Everything behind the animation: the plant, how it grows from a seed, its year, the fruit, where it grows, the species side by side, the family tree of the varieties and what each gives, harvest times around the world, the problems, shade and climate, and how far one tree’s crop goes.
Coffee is an evergreen shrub from the madder family (Rubiaceae, the gardenia’s family). Left alone, arabica grows into a tree of 9–10 m and liberica up to 20 m; farms keep it at about 2–3 m so people can reach the fruit. What we call a coffee bean is the seed of its cherry.
Arabica is grown from its own seeds; robusta and the new hybrids mostly from cuttings or grafts. Either way a farmer waits two to four years for the first crop, so planting coffee (or changing variety) is a long decision.
Arabica pollinates itself, so its seeds grow into the same variety (except unstable crosses like Pacamara). Robusta needs another plant’s pollen, so its seedlings all differ: farms copy their best trees by cuttings or grafts. F1 hybrids don’t come true from seed either and are cloned.
A cutting must come from an upright (orthotropic) shoot. Root a piece of a side branch and it grows sideways for ever, like the branch it came from.
On steep land, rows follow the level lines of the hill (found with an A-frame) so the rains don’t wash the soil and fertiliser away. One farm planted 2,400 trees on an acre in six days, with five people.
Tall varieties 3,000–4,000 trees per hectare, dwarfs like Caturra and Catuai 5,000–6,000, Kenya’s big SL trees and robusta 1,000–2,000 (often with several stems). Classic farms used 1,100–1,400.
An arabica shoot grafted onto a robusta root (the Nemaya rootstock) gets robusta’s resistance to nematodes, root-eating worms, and keeps arabica’s cup.
Fruit only grows on new wood, so trees are pruned after the harvest and topped at ≈ 2 m. After 6–8 crops many farms “stump” the tree at 30 cm and let two new shoots grow: a fresh tree on an old root in two years.
A grown tree follows the seasons: a dry spell, the blossom rain, three days of flowers, then seven to nine months for arabica’s cherries (nine to eleven for robusta) and the harvest. Close to the equator, where it rains most of the year, trees flower several times and are picked almost all year round.
Outer ring: this crop · inner: next year’s buds · drop: blossom rain · flower: 3 days
Buds form at the leaf joints and stop at a few millimetres. A few weeks of water stress make them ready; the first big rain then opens every tree on the hill together, 8–12 days later.
White, jasmine-scented, gone in 2–3 days. Arabica pollinates itself, so nearly every flower can fruit; robusta, liberica and the wild species need pollen from another plant, carried by bees and wind.
For ≈ 6 weeks the fruit hardly grows; then it swells fast (it needs water now: drought means small beans); then the bean fills in and hardens while the cherry stays green.
Every joint ripens at its own pace: one branch holds green, yellow, red and overripe cherries together. Careful farms pick each tree 3–5 times.
Most farms have one main harvest a year. Colombia’s trees flower twice: the main crop and the smaller “mitaca”. Kenya has a main and a fly crop; some robusta areas pick two or three times.
A coffee tree can carry buds, flowers, green and ripe cherries at the same time, especially where the rains are spread out.
Pickers are paid by the weight they bring in, so it is tempting to grab everything. Only fully ripe cherries make sweet coffee: the ripe ones are deep red (or deep yellow), a little soft, and come off with a gentle twist. Tap the cherries you would pick, then check.
A coffee cherry is about the size of a small grape, but most of it is seed: under the thin skin there is only a little sweet pulp (it tastes of honeydew melon), then sticky mucilage, the parchment shell, a silver skin, and two beans with their flat sides together.
In about one cherry in twenty only one seed grows: a round “peaberry” with no flat side. They are sorted out and sold on their own; some say they roast differently.
As it ripens the pulp fills with sugar, ≈ 18–24 °Brix when fully ripe. Overripe cherries turn dark and wrinkly and give fermented, unpleasant flavours.
Most varieties ripen red; some (Yellow Bourbon, Yellow Catuai) yellow, and red × yellow crosses can be orange. Colour doesn’t change the yield, but yellow fruit is harder to judge, so many farms avoided it.
The bitter caffeine keeps most insects away (robusta has about twice arabica’s), though the coffee berry borer lives on it. Cool highland farms keep pests away with cold instead.
The dried skin and pulp aren’t waste: brewed, they make cascara, a fruity “coffee cherry tea”. Home growers eat the fresh pulp or dry it for muesli.
About 5–6 kg of cherries make 1 kg of green coffee; more than 1,500 cherries go into a pound (450 g) of roasted beans.
Coffee grows in the “coffee belt” between the Tropics of Cancer and Capricorn, wherever there is a wet and a dry season and never frost. Altitude sets the temperature, about 0.6 °C cooler for every 100 m: arabica wants the cool mountain air, robusta the hot lowlands.
Cool air slows the cherries down: they take longer to ripen and pack more sugar and acids into denser, harder beans, with more fruit and flowers in the cup. Cold also keeps most pests away, so delicate varieties survive.
Near the equator (Colombia, Kenya, Ethiopia) the best arabica grows at 1,400–2,200 m; further from it (Brazil, Hawaii) the same coolness comes lower, at 800–1,200 m or even near sea level in Kona.
Coffee likes deep, well-drained, slightly acid soil rich in organic matter (volcanic soils are prized) and about 1,500–2,000 mm of rain a year for arabica, more for robusta, with a clear dry season.
Coffee can’t survive a hard frost. Brazil’s famous frosts (on its southern, higher farms) can wipe out a year’s crop and send world prices up.
Around 130 coffee species are known, most of them in Africa and Madagascar, and two make 99 % of the world’s coffee. Arabica is the child of two others: robusta crossed with eugenioides long ago, which is why arabica has four sets of chromosomes and can pollinate itself.
Leaves to scale with each other; cherries and beans drawn larger · bottom line: caffeine
About twice the caffeine, roughly half the sugar and less oil than arabica, and earthy pyrazines from roasting: bitter, woody, heavy-bodied, little acidity, and a thick crema that espresso blends like (often 3 arabica : 1 robusta).
From 25 % to about 40 % of world coffee since the early 1990s: it yields more, survives heat and rust better and costs less to grow. Well grown and processed, “fine robusta” is now finding its way into specialty coffee.
Big trees with big, uneven beans, grown in the Philippines (Barako), Malaysia and Indonesia. Excelsa, tart and fruity, is now counted as a liberica variety. Liberica coffee reached the World Barista Championship podium in 2021.
Nearly all the arabica outside Ethiopia descends from a few seeds taken from Yemen. A disease that beats one tree can beat them all, as phylloxera beat Europe’s vines in the 1860s. Wild species and Ethiopia’s forests are coffee’s reserve.
Stenophylla, rediscovered in Sierra Leone in 2018, tastes close to arabica yet grows about 6 °C warmer. Eugenioides (very low caffeine) and new F1 hybrids are other hopes.
Some wild species, such as Coffea charrieriana from Cameroon, make almost no caffeine; eugenioides has about a quarter of arabica’s.
Almost all the arabica grown outside Ethiopia comes from two lines that left Yemen: Typica (via India and Java to Amsterdam, Paris and the Caribbean) and Bourbon (via the island of Bourbon, now La Réunion, to East Africa and Brazil). Everything else is a natural mutation, a cross, a mix with robusta genes, or a new find from Ethiopia’s forests. Tap a name.
The variety decides the shape of the tree, the size of the leaves, fruit and beans, how much it yields, which diseases it resists and how good it can taste at its best. Farmers usually choose for yield and health first, roasters for flavour. Pick one to see its tree, its ratings and its story, or grow it on the stage.
Positions from World Coffee Research’s ratings (yield potential; quality potential at high altitude). Most varieties trade one for the other; the F1 hybrids (green) are bred to have both. Tap a dot.
Somewhere coffee is always being picked. North of the equator the main harvest falls roughly between October and March, south of it between April and September; close to the equator many countries have two crops a year.
From the regions in The World Atlas of Coffee (James Hoffmann): months, altitudes and main varieties vary from region to region inside a country.
Each is the Bourbon tree’s main season with one thing going wrong. Watch it on the stage, then press “Show the right way”.
First seen in East Africa in 1861; it ruined Sri Lanka’s coffee from 1869 within ten years (the island switched to tea), pushed Java to robusta, reached Brazil in 1970, Colombia in 1983 and caused a state of emergency in Central America in 2012–13.
Most rust-resistant arabicas got it from the same parent, the Timor Hybrid. New strains of rust now attack some of them (Lempira, Costa Rica 95), so breeders keep looking for new sources.
A fungus of East Africa that rots the green cherries. In 1968 it took half of Kenya’s crop, which led to the resistant Ruiru 11 (1985) and Batian (2010).
Nematodes are tiny worms that eat the roots (answer: grafting onto a robusta rootstock). Coffee wilt disease kills robusta in Uganda and Congo; resistant clones (KR1–KR10) were bred against it.
Coffee began as a forest plant in the shade of taller trees. In the 1970s many farms switched to dwarf varieties in full sun: higher yields, but more fertiliser and pesticide, more erosion and far fewer birds. Shade farms are coming back.
Forest coffee (wild trees in natural shade, low yields), garden coffee (a few trees round a homestead: most of Ethiopia’s crop) and plantation coffee (pruned, fertilised, selected varieties).
A Kenyan grower plants coffee with avocado, banana and climbing beans: the trees drop leaves that feed the soil (bananas bring potassium, beans nitrogen), pumpkins cover the ground, and no weeding or spraying is needed.
Warmer years move arabica uphill, help rust and the borer, and could make up to half of today’s coffee land unsuitable by 2050. Answers: shade, new varieties and F1 hybrids, robusta and other species, and moving farms higher.
About 12.5 million coffee farms, ≈ 95 % of them small family farms; around 125 million people live from coffee. Many earn too little: in 2019 the commodity price was about $1 per pound, the same as in 1980.
How far does one tree go? Pick a tree: its crop from the stage’s model goes through the mill (≈ 18–22 % of a cherry’s weight is green bean) and the roaster (≈ 16 % weight loss) into your cups.
A grown arabica tree gives roughly 2–6 kg of cherries a year depending on variety, age and care. Price points from the sources: a Kenyan smallholder was paid ≈ $3.18 per pound of green coffee, while his region’s coffee sold for $22.50 a 12 oz bag in the US.
Arabica makes a fine houseplant: glossy leaves, jasmine-scented flowers and, after three or four years, red cherries you can pick, pulp, dry and roast yourself.
Bright light with a wide view of the sky (an east, west or south window), or a grow light. In the garden: shelter from hot afternoon sun and drying winds.
Water when the top quarter of the pot is dry, then soak it. In hot, dry, windy weather a garden tree needs a deep watering twice a week.
Ordinary potting mix with some cactus mix or perlite for drainage; coffee likes it slightly acid. Feed in spring and summer; repot every 1–2 years.
Keep it warm and out of draughts; frost kills it. Brown leaf tips usually mean dry air or uneven watering: a humidifier or a tray of wet pebbles helps.
Fresh seed in its parchment, on damp potting mix with a little sand, covered with 1 cm of soil, kept warm: 6–8 weeks to sprout. Or let seeds sprout under a fruiting tree and pot them up.
Pick the red cherries, squeeze the beans out, soak them about a week (change the water when it clouds), dry them, rub off the parchment, roast in a pan until they crack, rest them a couple of days. Two backyard trees in Brisbane give about 2 kg a year.
In warm, wet places like Queensland, birds spread the seeds and coffee has become an environmental weed: check before you plant it outside.