Earthy
Wet forest floor, damp wood, cellar, moss. Almost all of it in tea comes from microbes rather than from soil, and the compound behind it is the same one you smell when rain hits dry ground.
- Sensed as
- aroma
- Compounds
- geosmin, and the methoxybenzenes formed during microbial fermentation
- Rises with
- pile fermentation, years of humid storage
- Falls with
- a rinse or two, and long clean dry storage
What it is
An aroma, heavy and low, arriving early and staying. In a good aged shou puer it reads as forest floor and old wood. In a badly stored one it slides toward mould, must and the smell of a damp cupboard, and the line between those two is the most consequential judgement on this axis.
Where it comes from
Geosmin, chiefly, produced by microorganisms and detectable by the human nose at extraordinarily low concentrations. It is the same compound responsible for petrichor and for the off-flavour in freshwater fish. Alongside it sit methoxybenzenes generated by microbial action during the pile fermentation of ripe puer, which contribute the stale, aged-wood side of the character. These are made by the microbes working on the leaf, which is why this axis belongs to fermented teas and essentially nowhere else.
Which teas show it
Ripe shou puer above all, where pile fermentation creates it deliberately. Aged sheng puer develops a gentler version over years. Other dark fermented teas such as liu bao and fu zhuan carry it. It is effectively absent from green, white, oolong and black teas, so an earthy note in one of those is usually a storage problem rather than a style.
How to turn it down
A proper rinse, sometimes two, removes the dustiest top note from a young shou. Beyond that, time in good storage does more than technique: a shou that is aggressively earthy at two years is often clean and sweet at eight.
How to turn it up
Cannot be created in the cup. What brewing can do is show it clearly: a rinse followed by hot, short infusions is the standard approach, and the rinse itself is worth smelling.
What it gets confused with
Roasted, because both are dark and warm, though one is applied heat and the other is microbial fermentation. Also confused with mustiness, which is not a variant of earthy but a fault: earthy is forest floor, musty is a wet cardboard box, and if a tea makes you think of a damp basement rather than a wood after rain, that is storage damage rather than character.
What people get wrong
Believing that earthiness comes from soil, or that a tea grown in rich earth tastes of it. It does not. The compounds are made by microbes during and after processing, and the terroir story attached to this axis is the least supportable of any. The other mistake is accepting every earthy note as authentic ageing. Some of it is a wet pile done badly or a cake stored somewhere humid, and no amount of patience improves that.
Sources
- Geosmin drives the earthy note in ripe puer, with methoxybenzenes produced by microbial action during pile fermentation. 'Exploring microbial and moist-heat effects on Pu-erh tea volatiles and understanding the methoxybenzene formation mechanism using molecular sensory science', Food Chemistry: X (2024)