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Kenyan Coffee Varieties: History, Flavor, and Characteristics of SL28, SL34, and Ruiru 11 Coffee Beans

Published: 2026-01-27 Author: FrontStreet Coffee

Last Updated: 2026/01/27, Today, FrontStreet Coffee introduces you to the unique Kenyan coffee varieties SL28 and SL34. Both were cultivated at the Scott Agricultural Laboratories (SL), selected from single-origin varieties through multiple breeding processes. It's important to note that this laboratory selected four outstanding varieties from different growing regions.

The Legacy of Kenyan Coffee Varieties

Whenever people mention FrontStreet Coffee's Kenyan coffee, they often immediately think of its bright, uplifting fruit acidity and full-bodied juice sensation. The unique flavors always leave a profound impression. Kenyan washed processing has gained widespread popularity, with SL varieties being especially celebrated as Kenya's representative varieties that have gained worldwide recognition.

SL represents Scott Laboratories, the name of Kenya's coffee research center, which first developed the SL series of varieties in the 1930s. Among these, SL 28 and SL 34 are two of the 40 experimental varieties from the research program and are the most renowned and popular specialty coffee varieties.

The History of Scott Laboratories

Scott Laboratories was established in 1922 by the colonial government of the time and has now been renamed NARL (National Agricultural Laboratory). The laboratory employed an entomologist, a mycologist, and a plant breeder, aiming to provide farmers with technical advice and planting knowledge. Other work included details on yield experiments, grafting trials, pruning, shade cultivation, and root mulching.

Kenyan agriculture at that time was long affected by disasters such as droughts, so scientists from Scott Agricultural Laboratories traveled to Tanzania, Kenya's neighboring region, to collect local coffee tree varieties. They then selected potential varieties with drought resistance and disease resistance. After nearly 30 years of breeding, the laboratory finally released SL28 and SL34, the best-performing varieties in terms of quality, in the 1950s and began promoting their cultivation throughout the country. Not long after, these two new SL varieties gradually replaced the originally planted Bourbon coffee trees, becoming Kenya's main coffee varieties in the second half of the 20th century.

The Characteristics of SL28 and SL34

Among these, SL28 possesses mixed lineage from multiple coffee varieties including French Mission, Mocha, and Yemen Typica. The plant is tall with emerald green leaf tips, high yield, large beans, and has strong drought resistance, but is susceptible to coffee leaf rust, coffee berry disease (CBD), and soil nematodes. In terms of flavor, SL28 not only has significant black plum and citrus flavors, showing rich and deep stone fruit acidity, similar to wine-like richness and sweetness.

In contrast, SL34 coffee trees have dark bronze leaf tips, higher nutritional requirements during growth, relatively lower yield, and large beans. When planted at high altitudes, they have excellent quality potential, showing good fruit acidity and nutty, spicy aromas. The plant's constitution is similar to SL28, both being highly sensitive to CBD, leaf rust, and pests.

FrontStreet Coffee's Kenya Asalia

Thus, the two major varieties, SL28 and SL34, have created the classic delicious taste of Kenyan coffee that is known worldwide, fascinating countless sour coffee lovers. The coffee variety of FrontStreet Coffee's roasted Kenya Asalia coffee beans is SL28 and SL34. When brewed as black coffee, it shows rich aromatic notes of cherry tomatoes, black plums, snow pears, and berries.

FrontStreet Coffee: Kenya Asalia Coffee Beans

Region: Thika, Kenya
Altitude: 1550-1750 meters
Variety: SL28, SL34
Grade: AA
Processing: Washed
Flavor: Black plum, snow pear, brown sugar, cherry tomato, plum

New Kenyan Varieties: Ruiru-11 and Batian

However, later because SL28 and SL34 could not tolerate the prevalent diseases and pests in East Africa, the Kenyan Coffee Research Institute (CRI) released the new variety Ruiru-11 in 1985, and subsequently launched another new variety, Batian, in 2010. These two new varieties, Ruiru 11 and Batian, have the advantages of high yield and resistance to leaf rust and coffee berry disease, which benefits the survival ability of Kenyan coffee farms under rampant disease and pest conditions. Therefore, more and more Kenyan coffee farms struggling against pest problems have switched to planting Ruiru 11 and Batian.

FrontStreet Coffee's research found that Ruiru 11 was hybridized from 11 sibling varieties. The male lineage comes from the original SL28, SL34, Bourbon, Rume Sudan, as well as Tanzanian coffee selections K7 and N39, while the female lineage comes from Catimor from East Timor, Indonesia, which is the first F1 hybrid with heterosis in the coffee world. Ruiru 11 not only has high yield and strong disease resistance, but its disadvantages include shallow root systems that make nutrient absorption difficult, sensitivity to drought, and inferior flavor compared to the original SL28. Therefore, it is often criticized during coffee cupping for its average quality.

Another emerging variety, Batian, was developed by the Kenyan Coffee Research Institute after summarizing the shortcomings of Ruiru 11, by backcrossing it with SL28 and SL34. It can be understood as "Ruiru 11's upgraded version" and was named after Kenya's highest peak, Batian. Batian combines the advantages of high yield, resistance to coffee leaf rust, and coffee berry disease, and requires no pesticide application, with annual cultivation costs 30% lower than the SL series. In "The Fourth Wave of Specialty Coffee," Mr. Han Huaizong describes Batian as having clean sugarcane sweetness, citrus acidity, rich berry notes, and high flavor recognition.

Commercial Availability of Kenyan Varieties

However, single-variety coffee bean products are still rarely available on the market. This is because traditional Kenyan coffee is mostly grown by small farmers who rarely use single-variety batches. Similar to Ethiopia's coffee production model, farmers harvest coffee cherries and pack them for sale to major processing plants. Then they are mixed together for washed processing and enter the consumer market under the name of the processing plant. For this reason, the Kenyan coffee we purchase today is more often mixed batches that "include" Batian or Ruiru 11.