SL34
General Characteristics
SL34 is one of the important coffee varieties selected in Kenya in the 1930s. It was chosen at Scott Agricultural Laboratories as part of a selection program conducted between 1935 and 1939, where all selected trees were prefixed with "SL".
Origin and Selection
SL34 was selected from a single tree growing on the Loresho Estate in Kabete (Kenya), in cooperation between Scott Laboratories and private plantation owners. This tree was designated as "French Mission".
The origin of French Mission is linked to the activities of French missionaries (known as Spiritans), who established a mission in 1893 in Bura (Taita Hills, Kenya), where they planted Bourbon coffee trees brought from La Réunion island. Seedlings from Bura were moved to a second French mission – Saint Austin (near Nairobi) in 1899, from where seeds made their way to coffee-growing settlers. This lineage is commonly known today as French Mission Coffee.
The Question of Genetics
Due to the historical migration path of beans directly from La Réunion, it is widely assumed that French Mission is a Bourbon variety. However, the latest genetic research has shown that SL34 is related to the Typica genetic group, not Bourbon.
This suggests that the story of SL34's origin from the French Mission population may be inaccurate or erroneous.
SL28
General Characteristics
SL28 is one of the most famous and valued coffee varieties originating from Africa. Since its selection in Kenya in the 1930s, SL28 has spread to other regions of the continent (it is particularly important in Arabica growing regions in Uganda) and also reached Latin America.
This variety thrives best at medium to high altitudes, is resistant to drought, but susceptible to major coffee diseases. One of its distinguishing features is its rusticity, meaning its ability to survive even years of neglect – after which it can start bearing fruit again. In Kenya, SL28 trees can be found that are 60–80 years old and still producing fruit.
History of Selection
SL28 was selected in 1935 by Scott Agricultural Laboratories (now the National Agricultural Research Laboratories – NARL) from a single tree belonging to a population known as Tanganyika Drought Resistant (a drought-resistant variety from Tanganyika). In 1931, the chief coffee inspector of Scott Labs, A.D. Trench, traveled to Tanganyika (now Tanzania), where he observed a coffee plant resistant to drought, diseases, and pests in the Moduli area. The collected seeds were brought to laboratories in Kenya, where their drought resistance was confirmed. From these efforts, SL28 was selected, proving to be the most valuable outcome of the intensive breeding work of that period.
The name "SL" comes from the designation of trees selected for research at Scott Laboratories between 1935 and 1939.
Genetic Origin
Recent genetic research has confirmed that SL28 belongs to the Bourbon genetic group, which confirms its high cup quality and the heritage of a valued Arabica lineage.
History of Scott Agricultural Laboratories
Scott Agricultural Laboratories were established by the colonial British government in Kenya in 1922. Their task was to conduct agricultural research, provide advice, and training for Kenyan farmers. The laboratories employed, among others, an entomologist, a mycologist, and a plant breeder.
The coffee section was moved to the laboratories in 1934 and had 24 acres of land dedicated to coffee cultivation. The unit's name came from the buildings – originally a sanatorium built in 1913, used as a war hospital during World War I, named after Dr. Henry Scott, a Scottish missionary. After being taken over by the Department of Agriculture, they were named Scott Agricultural Laboratories.
Both Scott Laboratories in Kenya and the research station in Lyamungo, Tanganyika, became key centers for coffee research in East Africa. Work was carried out in cooperation with private planters and included, among others, comparative trials, grafting, pruning, the effect of shading, and intercropping.
In 1944, it was decided to move coffee research to a new station at Jacaranda Estates (about 32 km north of Ruiru), which began operations in 1949. Additional stations were established in Upper Kiambu (1957), Meru (1958), Kitale (1938), Lake Victoria (1959), and Kisii (1957).
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