What is coffee terroir?

Terroir - borrowed from wine - refers to the complete set of environmental conditions that shape the character of a coffee from a specific place: altitude, soil composition, rainfall patterns, temperature range, topography, the varietals planted, and the processing traditions used. All of these interact to produce the flavour signature of a given origin.

It's why an SL28 from Nyeri can taste fundamentally different to an SL28 from Kirinyaga, even though it's the same variety grown less than 50 kilometres apart. The soil is different. The microclimate is different. The washing station management is different. Terroir names all those variables at once.

In specialty coffee, terroir is used more loosely than in wine, where it carries legal protection in many appellations. But the concept is genuinely useful - it explains why you can't simply plant the same variety somewhere else and expect the same results, and why the specific place a coffee comes from is part of what you're paying for.