A Short History of SL-28 & SL-34

Some coffee varieties happen by accident.

SL-28 and SL-34 didn't.

A coffee variety (or varietal) is simply a type of coffee tree, much like a grape variety in wine. 

These two were born from years of research, field trials and scientific obsession. Nearly a century later, they're still responsible for some of the world's most celebrated coffees.

So how did two experimental coffee trees become legends?

IT ALL STARTS IN A LAB

1922

Scott Agricultural Laboratories opens near Nairobi with one ambitious goal: find coffee varieties that can thrive in the often-challenging East Africa conditions while producing exceptional flavour.

Rather than creating new coffee plants, researchers spend years searching for exceptional trees already growing across the region. Their job isn't to invent greatness…it's to recognise it.

TWO STANDOUTS EMERGE

1931-1935

After evaluating hundreds of coffee trees, two selections rise above the rest.

One, descended from a drought-resistant population in neighbouring Tanganyika (modern-day Tanzania), stands out for its exceptional cup quality and resilience in drier conditions. The other impresses with its productivity and ability to flourish where rainfall is more reliable.

Their names don't exactly sound legendary. SL stands for Scott Laboratories, while 28 and 34 were simply the reference numbers assigned to two promising trees during the research programme. No grand naming ceremony. No hidden meaning. Just two lab selections that would go on to define Kenyan coffee (even though one isn’t technically Kenyan at all)!

KENYA FINDS IT’S SIGNATURE

1950s

As coffee production expands across Kenya, SL-28 and SL-34 become the country's benchmark varieties. They don't just influence what farmers grow—they define the flavour profile that makes Kenyan coffee famous.

Bright acidity. Juicy blackcurrant. Citrus sparkle. Exceptional sweetness.

Buyers around the world take notice. Demand for Kenyan coffee soars, its reputation for exceptional quality helping the country's finest lots achieve premium prices at auction and cementing Kenya's place as one of the world's most celebrated coffee origins.

STILL SETTING THE STANDARD

Today

Over 100 years after the first experiments began, SL-28 and SL-34 remain among specialty coffee's most celebrated varieties.

Newer varieties have since been developed with better resistance to pests and diseases, but when it comes to cup quality, SL-28 and SL-34 are still proving hard to beat.

Their genetics continue to influence breeding programmes around the world and their distinctive flavour profile still defines what many people think of when they picture a great Kenyan coffee.

Not bad for two lab rats….