Arabica is unusual among coffee species. It arose from a natural cross between two others, Coffea canephora and Coffea eugenioides, and carries four sets of chromosomes where most coffee species carry two. It is self-fertile, so a single tree can set seed. Those two facts explain much of its story: a species that came from a very small founding population, and whose cultivated forms descend from a handful of plants taken out of Ethiopia and Yemen, has very little genetic diversity to draw on.
Canephora, sold as robusta, is the opposite: it needs cross-pollination, it is genetically diverse, and it is naturally more resistant to several diseases. It contains roughly twice the caffeine of arabica.
Liberica is a large-fruited, large-leaved species grown mainly in parts of Southeast Asia and West Africa. Excelsa was long classified as a variety of liberica; a 2025 study led by researchers at Kew argued, on genetic and physical evidence, that it should be recognised as its own species, Coffea dewevrei. CoffeeHQ follows that treatment and notes that trade usage has not caught up.
Coffea stenophylla, from West Africa, was farmed until the early twentieth century and then largely forgotten. It was found again in the wild in Sierra Leone, and a 2021 study in Nature Plants reported that trained tasters judged it similar to high-quality arabica while it grows at mean temperatures several degrees higher. It is not yet a commercial crop, and yield and agronomy remain open questions.
Below the species is the variety, a distinct, heritable form; a cultivar is a variety selected and maintained in cultivation. In everyday coffee writing the two words are used almost interchangeably.
Most arabica grown outside Ethiopia descends from two lineages that left Yemen in the seventeenth and eighteenth centuries. Typica travelled through Asia to Europe and on to the Americas. Bourbon was taken to the island then called Bourbon, now Réunion, and spread from there. For two centuries, much of the world's arabica was one or the other.
Many familiar names are mutations or crosses within those lines. Caturra is a compact, high-yielding mutation of Bourbon found in Brazil. Mundo Novo is a natural cross of Typica and Bourbon, and Catuai is a cross of Mundo Novo and Caturra. Pacas and Villa Sarchi are other dwarf Bourbon mutations. Maragogipe is a large-seeded Typica mutation, and Pacamara a cross of Pacas and Maragogipe. SL28 and SL34 were selected in Kenya in the 1930s.
Outside these lines sit Ethiopian landraces — the vast, largely uncatalogued diversity of arabica in its home country, often sold simply as 'heirloom'. Gesha, also spelled Geisha, is the best known: collected in Ethiopia, grown without much notice in Central America, and made famous by a Panamanian farm in the 2000s for its intensely floral cup.
The traditional varieties are susceptible to leaf rust. The main source of resistance has been the Timor Hybrid, a natural cross between arabica and robusta found on the island of Timor, which is arabica-like but carries robusta's resistance genes. Crossing it with Caturra gave the Catimor group; crossing it with Villa Sarchi gave the Sarchimors. Colombia's Castillo and Kenya's Ruiru 11 and Batian come from related breeding programmes.
These varieties kept coffee farming viable in rust-affected regions. They also carried a reputation for a flatter cup, traced to their robusta ancestry. That reputation is contested: some blind comparisons have found little difference when the coffee is grown and processed well, and newer selections were bred with cup quality as a goal. It is fairer to say that resistance and quality were hard to combine than that they cannot be combined.
F1 hybrids are the most recent approach. They are first-generation crosses between genetically distant parents — often a rust-resistant line and an Ethiopian landrace — and tend to show strong vigour, yield and quality together. The catch is in the genetics: seed saved from an F1 plant does not reproduce the parent, so farmers must buy new plants raised by controlled crossing or tissue culture, which costs more and requires a trustworthy nursery.
A caution about variety names on bags. Variety influences the cup, but the same variety grown in two places can taste very different, and names are sometimes applied loosely. Treat the variety as one piece of evidence.
Your task. Open the arabica and robusta pages and find the production split. Then open three variety pages you have seen on bags and, for each, write down its parent or lineage and one thing the page says is uncertain.
What to notice. Nearly every familiar arabica variety traces to two lineages, and most pages carry a caveat. A narrow family tree is a fact about coffee, not a gap in the reference.
Exercise: Arabica beside robusta
Objective. Taste the difference between the two species that make up almost all the coffee in the world.
You will need
One coffee labelled 100% arabica and one that is 100% robusta, or a blend that states its robusta share
Cupping bowls or your usual brewer, two cups
Keep the same
Same recipe and water
As similar a roast level as you can find — this is the hard part
Procedure
Look at the beans first: shape, size and the line of the centre cut.
Brew both the same way.
Smell, then taste, side by side.
Describe body, bitterness and acidity for each.
What to notice
Which is more bitter? Which has more acidity?
Which is heavier in the mouth?
Do the beans look different?
Reading what you found
Robusta is commonly described as heavier, more bitter and lower in acidity, and it contains more caffeine, which is itself bitter. If your robusta is also roasted darker than your arabica, much of what you taste may be roast. Well-processed robusta exists and can upset the textbook description, which is worth knowing first-hand.
What this cannot show
Two bags cannot separate species from roast, processing and quality grade.
Pure robusta can be hard to buy at retail; a stated blend is an acceptable substitute but weakens the comparison.
A protocol for you to run. CoffeeHQ has not run it and reports no result from it.
A smallholder in a region where leaf rust is established has to replant half the farm. A buyer has offered a premium for Bourbon. A neighbour replanted with a resistant Catimor-type variety and lost nothing in the last outbreak.
Reasoning it out
Bourbon may earn a premium in a good year, and in a rust year may yield very little.
The resistant variety protects yield; any price discount depends on the buyer and on how well it is grown and processed.
An F1 hybrid might offer both, but costs more per plant and cannot be propagated from saved seed.
The decision is about risk and cash flow over several years, not about which variety is 'best'.
What to do
There is no universally right answer, which is the point. Many farmers split the risk: resistant varieties on most of the land for security, and a smaller plot of a prized variety for the premium market. When a drinker says one variety is simply better, they are describing the cup and ignoring the farm.
World Coffee Research variety and agronomy resources — World Coffee Research (WCR)
Royal Botanic Gardens, Kew — peer-reviewed research on Coffea species — Royal Botanic Gardens, Kew (A. P. Davis and colleagues)
Sections are labelled with the kind of claim they make. How CoffeeHQ uses sources, and what each one is relied on for, is set out in the source and evidence policy.
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