The word cotton points to a botanical genus called Gossypium, comprising several dozen species, of which only four are cultivated commercially. Of those four, two account for nearly all of the cotton produced in the world. Gossypium hirsutum, native to the Americas and now grown across most cotton-producing regions, makes up roughly 90% of global cotton supply. Gossypium barbadense, native to South America and the Caribbean, makes up most of the remaining 8%.
The cotton in a typical T-shirt — the cotton in the towels at most hotels, in the sheets in most homes, in the denim of most jeans — is G. hirsutum. It is what the trade calls "upland cotton" or, sometimes, "standard cotton." It is the world's commodity fiber.
The cotton in the small fraction of garments that wear differently, that drape differently, that age differently — Egyptian Giza, American Supima, and Peruvian Pima — is G. barbadense. A different species. Closer in genus, distant in property. Different fiber.
This article is about that distance. About what barbadense cotton is, why it behaves the way it does, and why the small genetic difference between two cotton species produces, in a finished garment, the experiential difference between a shirt that wears in and a shirt that wears out.
The difference between Pima cotton and standard cotton is not large in the way that the difference between cotton and silk is large. It is small. It is measurable in millimeters and micronaires, in dollars per kilogram of fiber, in years of garment life. Most consumers, holding two T-shirts in a store, would not be able to distinguish them on inspection alone.
The difference becomes visible over time. A Pima shirt and a hirsutum shirt, identical at the moment of purchase, separate slowly. Six months in: the hirsutum shirt has the first traces of pilling on the inside of the upper arm. A year in: its collar curls slightly and its color has shifted toward warm gray. Three years in: the hirsutum shirt is in the rag pile.
The Pima shirt, washed alongside it for the same three years, looks like a Pima shirt that has been worn for three years. The cuffs are crisp. The color has held. The cloth has softened on the surface but stayed dense in the body.
This is the difference. It is small, slow, and worth paying attention to.