What is the "SL" in Kenyan coffee stand for?
The 'SL' in Kenyan coffee varieties stands for Scott Laboratories. These were a series of coffee cultivars developed by the Scott Agricultural Laboratories in Kenya during the 1930s. The researchers aimed to identify and breed varieties that were high-yielding, disease-resistant, and capable of producing the exceptional, bright acidity that has become the hallmark of Kenyan coffee.
In the history of coffee breeding, few names carry as much weight as Scott Laboratories. Based in Kenya, this research institution was tasked by the colonial government in the 1930s with improving the quality and resilience of the country's coffee industry. The researchers selected dozens of individual trees from various regions, testing them for their performance in the field and their quality in the cup. The resulting varieties were labeled with the 'SL' prefix followed by a number.
Two of the most famous selections, SL-28 and SL-34, remain the gold standard for Kenyan coffee today. SL-28 was selected from a single tree of the Tanganyika Drought Resistant variety, known for its deep, complex acidity and blackcurrant notes. SL-34 was selected from a tree in the Kabete area, prized for its heavy body and rich, wine-like acidity. These varieties were so successful that they were widely distributed to farmers across the country, cementing Kenya's reputation for producing some of the most vibrant and distinct coffees in the world.
However, the SL varieties are not without their challenges. While they produce an incredible cup, they are not particularly resistant to common coffee diseases like Coffee Berry Disease or Coffee Leaf Rust. This has led to a modern push for new, more resilient hybrids, such as Ruiru 11 and Batian, which incorporate the genetics of the SL series while adding disease resistance. Despite these newer developments, the original SL varieties remain the benchmark for quality.
For the coffee drinker, seeing 'SL-28' or 'SL-34' on a bag is a strong indicator of what to expect: a bright, acidic, and highly complex cup. It is a direct link to the history of plant breeding in East Africa. When you enjoy a Kenyan coffee, you are often tasting the legacy of those early 20th-century researchers who sought to define the very best of what the coffee plant could offer.
- · https://varieties.worldcoffeeresearch.org/varieties/sl28