Two species, one drink
Coffee comes from the seeds of a flowering shrub. There are more than a hundred species in the coffee family, but nearly all the coffee people drink comes from two of them: Coffea arabica, called arabica, and Coffea canephora, best known by its trade name, robusta.
Arabica makes up the larger share of world production. Robusta makes up most of the rest. Within each species there are many varieties, the way there are many kinds of apple, and how a coffee is grown, processed and roasted changes its flavor as much as the species does. Still, the species sets the starting point, and the differences are real.
Arabica vs robusta at a glance
| Arabica | Robusta | |
|---|---|---|
| Species | Coffea arabica | Coffea canephora |
| Typical altitude | Higher, often about 600 to 2,000 meters | Lower, often from sea level to about 800 meters |
| Climate | Cooler, milder | Hotter, more humid |
| Plant | More delicate, more prone to pests and disease | Hardier, higher yield |
| Caffeine | Lower, roughly 1 to 1.5 percent of the bean | Higher, roughly twice arabica |
| Bean shape | Oval, with a curved center line | Rounder, smaller, with a straighter line |
| Taste | Sweeter, more aromatic, brighter acidity | Heavier, more bitter, earthy or nutty |
| Price | Higher | Lower |
| Common uses | Most specialty and everyday coffee | Instant coffee, some espresso blends |
All of these are general patterns. Altitude ranges vary by country and latitude, and caffeine figures vary by variety and by how they are measured. Treat the numbers as a guide, not a rule.
The plants and where they grow
Arabica likes it cool. It does best in the highlands of the tropics, where warm days and cool nights slow the ripening of the coffee cherry. Slower ripening gives the seed more time to develop sugars and aromatic compounds, which is a big part of why high grown arabica is prized. The trade off is that arabica is fussy. It is more vulnerable to pests, to diseases like coffee leaf rust, and to swings in weather.
Robusta earned its name. It grows at lower, hotter elevations, tolerates more heat and humidity, resists many of the diseases that trouble arabica, and produces more fruit per plant. That makes it easier and cheaper to farm, which shapes everything that follows, from price to how it gets used.
There is a botanical difference too. Arabica can pollinate itself, so its varieties stay fairly stable from one generation to the next. Robusta needs pollen from another plant, so it varies more across a farm.
Caffeine: roughly double
This is the difference most people have heard about, and it holds up. As an approximate general figure, robusta beans carry about twice the caffeine of arabica beans by weight. Caffeine tastes bitter, and it also helps protect the plant from insects, which is one reason the hardier species carries more of it.
Two practical points follow. First, if a coffee tastes noticeably bitter and gives you more of a jolt than expected, robusta in the blend is a likely reason. Second, species matters far more for caffeine than roast level does. A dark roast arabica and a light roast arabica are close. An arabica and a robusta are not. We cover that in more detail in does dark roast have more caffeine.
How they taste
Arabica tends to taste sweeter and more aromatic, with more perceived acidity. Depending on where it grows and how it is roasted, that can read as fruity, chocolatey, floral or nutty. It is the species behind most coffee shop drip, pour over and specialty espresso.
Robusta tends to taste heavier and more bitter, with less acidity and less sweetness. Words like earthy, woody, grainy or rubbery come up, especially with lower quality lots. That reputation is partly earned and partly about how robusta has been farmed and processed. Carefully grown and processed robusta exists, and it can be pleasant, with a deep, cocoa like heaviness. But most robusta on the market is grown for volume, not flavor.
The label tells you less than you think. "100% arabica" means the coffee contains no robusta. It does not tell you how fresh it is, how well it was grown or how it was roasted. A stale arabica will taste worse than a fresh, well made blend.
Price and why robusta shows up in espresso
Arabica costs more because it is harder to grow: higher land, lower yields, more risk from disease and weather. Robusta is cheaper to produce, which is why it dominates instant coffee and appears in many lower priced supermarket blends.
Price is not the only reason roasters use it, though. Many espresso blends, especially in the Italian tradition, include a share of robusta on purpose. In a small, concentrated shot it brings:
- Thicker crema. Robusta tends to produce a heavier, longer lasting layer of crema on top of the shot.
- Body and weight. It adds a heavier mouthfeel that holds up under milk.
- Bitterness that cuts through milk. In a cappuccino or latte, a little robusta keeps the coffee flavor from getting lost.
- A stronger kick. More caffeine per shot.
Other espresso blends are all arabica and aim for sweetness and clarity instead. Neither approach is wrong. It depends on whether you drink your espresso straight or with milk, and whether you prefer a bright shot or a heavy, bittersweet one. Vietnamese coffee, made strong and sweetened with condensed milk, is another place robusta is traditional, and you can read more in what is Vietnamese coffee.
Which should you buy?
- For drip, pour over and French press: arabica or an arabica led blend gives the most sweetness and aroma.
- For espresso with milk: a blend with some body, with or without a little robusta, holds its flavor through the milk.
- For more caffeine: robusta or a robusta blend, or simply a bigger dose of what you already like.
- For any of them: freshness matters as much as species. Buy recently roasted coffee in an amount you will finish.