SL34
A variety selected alongside SL28 in Kenya by Scott Agricultural Laboratories, widely grown alongside it in Kenyan coffee-growing areas and generally better suited to higher-rainfall conditions.
In short
SL34 is an arabica variety selected in Kenya in the late 1930s, grown mostly in that country and usually sold together with its better-known sibling, SL28. It is a tall plant with large beans whose quality the World Coffee Research catalogue rates as exceptional.
It also carries a small mystery. Its recorded origin points to Bourbon, and genetic testing points to Typica.
A label that does not match the genetics
Sourced
According to the catalogue, SL34 was selected at Scott Agricultural Laboratories from a single tree on the Loresho Estate in Kabete that was labelled French Mission. It describes the variety as adapted to high-altitude areas with good rainfall. French Mission is the name given to coffee descended from Bourbon seed brought to Kenya by French missionaries in the 1890s, so SL34 was long assumed to be a Bourbon type.
Genetic testing has since indicated that SL34 belongs with Typica. The catalogue records both facts. The likeliest reading is that the original tree was not what its label said, which is a useful reminder of how much variety history rests on old paperwork.
The catalogue entry
Sourced
| Variable | Typical range | What moving it does |
|---|---|---|
| Stature | Tall | |
| Genetic group | Bourbon and Typica group, Typica related | |
| Yield potential | Medium to low | |
| Quality potential at high altitude | Exceptional | |
| Bean size | Large | |
| Leaf tip colour | Dark bronze | |
| Coffee leaf rust | Susceptible | |
| Coffee berry disease | Susceptible | The catalogue singles this out as a serious weakness. |
| Nematodes | Susceptible |
As listed in the World Coffee Research catalogue.
How it differs from SL28
Sourced
- SL28 — Bourbon-like where SL34 is Typica-like, green leaf tips where SL34's are dark bronze, noted for drought tolerance, and rated a little lower for yield.
- Typica — The lineage genetic testing assigns SL34 to. Both are tall, large-beaned and disease-susceptible.
- Bourbon — The lineage SL34's French Mission label implied. The two share a history in Kenya but not, it appears, a pedigree.
What this means for a bag of Kenyan coffee
CoffeeHQ explanation
Most Kenyan coffee is grown by smallholders who deliver cherries to a shared washing station, where lots from many farms and several varieties are combined. A bag labelled SL28 and SL34 is describing the predominant plantings, not a laboratory analysis, and resistant varieties such as Ruiru 11 and Batian are often present as well.
For a drinker the two SL selections are effectively a single style. The differences between them matter to farmers, who see them in the field, far more than to anyone tasting the result.
One of those field differences is worth knowing because it explains the variety's decline. The catalogue describes SL34 as highly susceptible to coffee berry disease, a fungus that attacks the developing fruit and can destroy much of a crop in a wet season. A farmer without the means to spray is taking a real risk by keeping it.
Reputation in the cup
Tendency, not a guarantee
SL34 shares the reputation of Kenyan coffee generally: vivid acidity, pronounced fruit and a heavy, juicy body. It is often said to be the slightly fuller and less sharply acidic of the pair, though that is trade lore and not something the catalogue records. Altitude, soils and Kenyan washed processing contribute at least as much as the variety.
What to do next
- Coffee from Kenya — How Kenyan coffee is grown, processed, graded and sold.
- SL28 — The companion selection and the more widely planted of the two.
- Origin and traceability terms — What a label can and cannot tell you about what is in the bag.
- Become a coffee expert — A structured programme from the plant and its processing to roasting, water and tasting.
Where SL34 is documented in the atlas
Only countries CoffeeHQ has written an entry for, and only where a document it has read names SL34 there. This is not a list of everywhere it is grown.
- Kenya. Selected in Kenya in the late 1930s from a tree on the Loresho Estate at Kabete; named in the same 2022 study. Source: Coffee Varieties Catalog: arabica and robusta entries, with the histories of each.
Commonly grown in
Learn it as a course
The Coffee Expert lesson Species and varieties covers this ground in order, with exercises you can do at home.