SL28

The SL28 variety stands as one of the most iconic and influential cultivars in the history of specialty coffee. Its name is derived from the Scott Agricultural Laboratories (SL), a research facility commissioned by the Kenyan government in the 1930s to identify and catalog coffee varieties that could thrive in the region's specific climate. Between 1935 and 1939, researchers at the lab conducted single-tree selections to isolate plants that demonstrated superior productivity and resilience, resulting in the identification of the SL28 lineage.

Genetically, SL28 is widely recognized for having a Bourbon-like background, though its exact parentage remains a subject of historical discussion. It was originally selected from a plant known as 'Tanganyika Drought Resistant,' which was discovered near Lake Tanganyika. This heritage provided the variety with a notable ability to withstand drought conditions and adapt to high-altitude environments, making it a cornerstone of Kenyan coffee production for decades.

For farmers, the appeal of SL28 has historically been its balance of high yield potential and remarkable cup quality. The plant is characterized by its tall stature and broad leaves, which often display a distinct bronze or reddish tint at the tips. While it is celebrated for its agronomic performance in specific East African climates, it is also known to be susceptible to major coffee diseases, such as coffee leaf rust, which has led to ongoing efforts in breeding and variety management to protect the crop's future.

To the roaster and the drinker, SL28 is synonymous with the classic 'Kenyan profile.' It is frequently cited for its intense, vibrant acidity and a heavy, wine-like mouthfeel. Common sensory descriptors associated with the variety include blackcurrant, pomegranate, and hibiscus. Because of these unique organoleptic properties, SL28 is highly sought after in the specialty market, often appearing as a single-variety separation in high-end coffee offerings.

In the broader context of coffee science, SL28 serves as a vital genetic resource. It has been included in global performance trials, such as the World Coffee Research International Multilocation Variety Trial, to better understand how its traits perform across different environments. Its genetic legacy also continues through modern breeding programs; for instance, it was used as a parent in the development of the Batian variety, which was released by the Kenyan Coffee Institute to improve disease resistance while maintaining the quality profile of its predecessor.

Today, the story of SL28 is one of preservation and appreciation. While newer, more disease-resistant hybrids are being introduced to combat the challenges of climate change and agricultural pests, the industry remains deeply committed to the SL28 profile. Projects focusing on pure SL28 separations allow the industry to explore the full potential of this historic variety, ensuring that its unique contribution to the sensory landscape of coffee remains available to future generations.