Coffea arabica, the species behind essentially all specialty coffee. When a bag lists an origin, a farm, an altitude and a variety, it is talking about arabica — the species is so assumed that most specialty bags never bother to print it.
Arabica is the fussier of the two species people drink. It wants altitude, shade, a narrow temperature band, and it is vulnerable to leaf rust and to the coffee borer beetle. In exchange it produces the sugars, acids and aromatic precursors that make a cup taste of jasmine or blackcurrant or peach instead of just tasting of coffee.
Where the flavour comes from
Arabica carries roughly 60 % more lipids and nearly twice the sugar of robusta. Those are the raw material the roast works with: sugars caramelise, lipids carry aroma. It also has about half the caffeine — caffeine is bitter, so less of it means more room for everything else.
That's the whole story of why specialty is arabica. Not snobbery: there is simply more to extract that anyone wants to taste.
Arabica is not one thing
The species splits into varieties — Typica, Bourbon, Caturra, SL28, Geisha — and the gap between them is enormous. A Panamanian Geisha and a Brazilian Bourbon are the same species and taste nothing alike. That's the level at which specialty actually shops, and it's covered in varietals.
Ethiopia is the genetic homeland; the "heirloom" on an Ethiopian bag means a local landrace nobody has formally catalogued, of which there are thousands.
What it means for your brewing
Nothing directly — every recipe in this app assumes arabica. It matters when you meet a coffee that isn't: a blend cut with robusta will extract faster, taste flatter, and forgive less than the recipe expects.
