Iris

What it is

The rhizome, not the flower. Roots are lifted, dried for two to three years so the irones develop, then distilled, and the yield is tiny. Orris butter is the most expensive natural in regular use.

What it smells like

Cool, powdery and faintly rooty, closer to damp clay or face powder than to anything growing. It reads as expensive and a little severe, and people meeting it for the first time often describe it as smelling of nothing, which is itself the effect.

Where it sits

Which layer of the pyramid it is listed in, across every fragrance here that carries it. A base note is one you smell for hours; a top note is usually gone within the first.

What it turns up with

How much more often than the catalogue average. 1.0x would be chance, so these are the things that genuinely travel with it rather than the things that are simply common.

When it is worn

Against the average fragrance here. The line marks that average, so a bar past it means this is worn in that season or setting more than most.

Houses that use it most

Counted across the fragrances here, which reflects what we cover as much as what a house makes.

Chanel (13), Prada (13), Lancome (12), Givenchy (11), Guerlain (9), Xerjoff (8).