What is the difference between SL-28 and SL-34?

The 'SL' in SL-28 and SL-34 stands for Scott Laboratories, a research organization commissioned by the Kenyan government in the 1930s to identify coffee varieties that could thrive in the country's unique climate. These two cultivars have since become the backbone of the Kenyan coffee industry, celebrated globally for their distinct, high-quality flavor profiles that define the 'Kenyan' cup.

SL-28 is arguably the most famous of the two. It was selected from a drought-resistant variety originally found in Tanganyika (modern-day Tanzania). Its primary claim to fame is its incredible cup quality, characterized by a bright, sparkling acidity and intense notes of blackcurrant, citrus, and tomato. However, from an agronomic perspective, SL-28 is notoriously delicate. It is highly susceptible to Coffee Berry Disease (CBD) and leaf rust, requiring significant care and ideal growing conditions to produce a healthy yield.

SL-34, on the other hand, was selected from a single tree found in the Loresho Estate in Kabete, Kenya. While it shares the high-quality potential of SL-28, its flavor profile leans toward a heavier, more syrupy body and a deep, wine-like complexity. It is often described as having a more 'rounded' acidity compared to the sharp, pointed brightness of SL-28. Agronomically, SL-34 is slightly more robust and adaptable, often performing well at a wider range of altitudes, though it remains vulnerable to the same common coffee diseases.

In the cup, roasters and baristas often blend these two varieties to achieve a balance between the bright, fruit-forward acidity of SL-28 and the rich, heavy mouthfeel of SL-34. Because they are so closely linked to the terroir of Kenya, they are rarely grown with the same success elsewhere, making them a true hallmark of the region's coffee identity.

For the reader, understanding these varieties helps explain why Kenyan coffee is so consistently distinct. When you see 'SL-28' or 'SL-34' on a bag, you are looking at a piece of agricultural history that has been carefully preserved for nearly a century. They represent a commitment to quality over quantity, prioritizing the sensory experience of the final brew above the ease of farming.