SL28 and SL34 Coffee, Explained: Kenya's Legendary Varieties

6 min read · Updated June 21, 2026

What SL28 and SL34 are, how the two Kenyan varieties are alike and different, the other SL selections, why they're so popular, and how to buy and brew them.

Some coffee names sound romantic: Gesha, Bourbon, Typica. Then there are SL28 and SL34, which sound like parts from an engineering catalog and taste like blackcurrant, citrus, flowers, and lightning in a cup. They are the varieties behind much of what people mean by “classic Kenyan coffee.”

This guide covers what SL28 and SL34 are, where they came from, how they’re alike and different, the other SL varieties, why these two became the famous ones, and how to buy and brew them.

What SL28 and SL34 are

SL stands for Scott Agricultural Laboratories, the Kenyan research station where they were selected in the 1930s. The numbers are selection numbers, so SL28 and SL34 read like lab IDs because that is exactly what they are. Both are tall Arabica varieties, and both have been grown in Kenya for close to 90 years.

They are also the backbone of the country’s coffee. By one widely cited estimate, SL varieties make up around 80% of Kenyan coffee. When a specialty bag says “Kenya, washed, SL28/SL34,” you’re looking at the heart of that tradition.

Where they came from

SL28 was selected in 1935 from a single tree in a population called Tanganyika Drought Resistant, after a Scott Labs officer noticed drought-tolerant plants on a tour of what is now Tanzania. World Coffee Research places it in the Bourbon group, and notes it is rustic enough that some SL28 trees in Kenya are 60 to 80 years old and still producing.

SL34 was selected from a tree on the Loresho Estate in Kabete, Kenya, originally labeled “French Mission,” a name tied to Bourbon coffee carried through French missionary networks. Here’s the twist: WCR’s genetic testing indicates SL34 is actually related to the Typica group, despite that Bourbon-flavored backstory. It’s a good reminder that coffee variety history blends farm records, colonial-era notes, oral tradition, and modern DNA, and the story on a bag often simplifies a tangled history.

SL28 vs SL34: alike and different

They’re sibling-like. Both are tall, large-beaned Arabicas that can produce exceptional cups at high altitude, both anchor the bright, juicy, fruit-forward Kenyan profile, and both share the same weakness: susceptibility to coffee leaf rust, coffee berry disease, and nematodes.

Where they diverge:

So SL28 leans toward the lightning-bolt version of Kenyan acidity, and SL34 toward a slightly rounder, fuller cup. Both still want to be brewed for clarity and sweetness.

Can you actually taste the difference?

Sometimes, but not reliably. A clean side-by-side of pure SL28 and pure SL34 from the same farm, altitude, process, and roast would be a great experiment, and it’s also rare. Most Kenyan lots, especially from smallholders and cooperative washing stations, are mixtures of varieties, often SL28, SL34, Ruiru 11, and sometimes Batian, because small farms aggregate cherry and separating by variety is rarely practical.

So, for a home brewer: SL28 is often described as brighter and more blackcurrant-heavy, and SL34 as fuller and rounder, but in real bags they’re usually blended. What you’re tasting is the broader Kenyan SL profile more than a clean one-variety comparison.

What about the other SL varieties?

Scott Labs made many selections in the 1930s. SL is a research prefix rather than a flavor family, and most of those numbers never became household names in specialty coffee. The one worth knowing is SL14.

SL14 was selected around 1936 from a tree labeled “Drought Resistant II.” It’s a tall, Typica-related variety valued for drought and cold tolerance, grown mostly in Kenya and Uganda. It earns its place agronomically, since it holds up where conditions are tougher. It stayed in SL28 and SL34’s shadow because it carries less of their cup reputation, so you’ll see it more as a hardy field variety than a headline on a specialty bag.

Why SL28 and SL34 became the famous ones

A few reasons stack up:

• Cup quality at altitude. Grown high and processed well, they produce some of the most recognizable coffee on earth.
• A memorable flavor identity. Currant, citrus, cranberry, grapefruit, winey acidity, florals, and a juicy body give roasters and drinkers something specific to talk about.
• Scale and exposure. They were planted and exported widely, so specialty roasters met them again and again. A variety can only get famous if people keep drinking it.
• Processing synergy. Kenya’s washed tradition emphasizes clarity and acidity, which is exactly where SL28 and SL34 shine. See processing methods.
• A good story. Like Sudan Rume and Gesha, these varieties carry narrative tension: great flavor paired with real farming difficulty.

SL14, by contrast, won on toughness more than fame, which is why SL28 and SL34 are the names that stuck.

The catch: disease and farmer economics

The same varieties enthusiasts chase are difficult to grow. SL28 and SL34 are susceptible to coffee leaf rust, coffee berry disease, and nematodes, which makes them riskier and costlier to maintain than newer Kenyan varieties bred for resistance, like Ruiru 11 and Batian. Some farms lose real volume to disease pressure, and the resistant varieties are easier on a grower’s margins.

That tension is part of why SL28 and SL34 feel romantic. They’re older, flavor-first cultivars that demand more care, grown in a world that keeps inventing hardier options. When you drink a great Kenyan SL coffee, you’re tasting a choice a farmer made to prioritize the cup.

How to buy and brew it

On the bag, look for Kenya, washed, SL28/SL34, and a region such as Nyeri, Kirinyaga, Embu, Murang’a, Kiambu, or Meru. The grades you’ll see, AA, AB, PB, and the rest, describe bean screen size and shape, not cup quality (PB is peaberry). AA and AB can both be excellent, and AB is often good value. Expect a mixed-variety lot more often than a pure single-variety separation.

To brew, treat it like a dense, high-acid washed African coffee and aim for clarity:

• A V60 or Kalita, a 1:16 to 1:17 ratio, water around 93–96°C, and a medium-fine grind.
• A starting point: 16 g coffee, 264 g water, 94°C, a 45 g bloom for 45 seconds, then pours to 150 g, 220 g, and 264 g, finishing around 2:45–3:30.
• If the cup is sharp, thin, or sour, grind finer or go a little hotter. If it’s harsh or drying, ease the agitation, grind coarser, or drop the temperature a touch.

For the mechanics, see grind size, brew temperature, extraction, and resting.

Track it in BeanBench

Because most Kenyan lots are blends and every farm brews up differently, your own notes beat any generic flavor chart. In BeanBench you can log the variety, region, grade, process, roast date and rest, your grind and water, and tasting notes, then your rating, so you learn which Kenyan coffees actually land for you. From here, read up on coffee varieties, Sudan Rume, and processing methods, or pick a recipe.