What is SL-28 Coffee? Taste, Origin & Brewing Guide

Last updated: 20 May 2026

What is SL28 Coffee?

SL28 is a variety of coffee most commonly grown in Kenya. It is a legacy of agricultural research conducted by Scott Agricultural Laboratories under British colonial rule in the 1930s, initially selected for its drought and disease resistance. Today, it is known for producing cups of exceptional quality, which has led to it being grown in a wide range of countries, especially in Latin America.

What Does SL28 Taste Like?

Much like Gesha, SL28 is one of those varieties that carries a recognisable hallmark regardless of where it is grown. In the case of SL28, that hallmark is often plump, juicy notes of blackcurrant, blackberry, strawberry and bright citrus notes of lemon or lime. It tends to be a well-structured cup with a fuller, sometimes syrupy, mouthfeel.

Washed SL28

Washed lots are where you tend to find those key SL28 qualities, especially as washed processing is the primary method used in Kenyan washing stations. Usually, the acidity is crisp and defined, with a citric structure similar to red berries, lemon or lime.

SL28 is naturally sweet, often showing purple berry characteristics such as blackcurrant and blackberry. There can occasionally be floral and tea-like notes too, similar to black Assam tea.

Natural SL28

Natural processing is less common than washed processing for this variety, and is more commonly produced in Latin American countries such as Peru and Costa Rica rather than Africa.

Natural processing tends to highlight the sweetness and body of SL28. The bright, fresh berry notes of a washed SL28 often come across as a sweeter and less acidic jammy note, similar to blackcurrant or blackberry jam. Usually, a natural process will bring out a wine-like quality in both the finish and the body.

Honey SL28

Honey processing marries the brightness of washed coffee with the structure and sweetness of natural coffee. Honey-processed SL28 often has bright, crisp blackcurrant notes, with a more syrupy body, distinct sweetness and a softer citric acidity that more closely resembles tangerine.

Photo: Natural SL28 processing in Uganda on raised beds (Omwani).

What is the Origin of SL28?

SL28 traces back to 1930s Kenya, which was under British colonial rule at the time. Scott Agricultural Laboratories, often referred to as Scott Labs, was founded in the early 20th century by the Kenya Colonial Administration.

A senior officer at Scott Labs called A.D. Trench found a particularly drought and disease-resistant plant during a research trip in Tanganyika, modern-day Tanzania. Seeds were collected and brought back to Scott Labs, where the selection was named “Tanganyika Drought Resistant”.

Throughout the mid-to-late 1930s, Scott Labs evaluated 42 different trees for drought tolerance, disease and pest resistance, yield and cup quality. The varieties were named with the “SL” prefix from “Scott Laboratories”, with the number referring to the selection sequence.

Because of SL28’s impressive resilience and high cup quality, seeds were distributed across Kenya and the variety has remained significant ever since.

Recent genetic testing suggests SL28 has Bourbon ancestry, with some research suggesting it may also contain Sudan Rume ancestry. This would help explain its elevated, sweet cup profile, as well as its unusually high tolerance to drought.

Where is SL28 Grown?

SL28 thrives in East African growing regions. It is primarily grown throughout the central and eastern regions of Kenya, the birthplace of SL28, but has also expanded to other high-altitude regions such as Uganda and Malawi.

Due to SL28’s reputation for phenomenal cup quality, some experimental farmers in Central and South America have also chosen to grow SL28 on their own farms. Colombia, Costa Rica, Guatemala and El Salvador have all produced notable SL28 lots.

While SL28 is quite adaptable, it grows best at high altitudes between 1,500 and 2,200 metres above sea level. Growing this variety in a cool climate allows the cherries to have a longer maturation time, which helps the coffee build sugars and develop more complex flavours.

How is SL28 Grown and Harvested?

SL28 grows best in nutrient-rich soil, especially the volcanic loams of East Africa. Careful pruning is necessary for consistent yields, with the central canopy kept clear for improved airflow and sunlight. While SL28 is drought-resistant, it is now more susceptible to coffee leaf rust and coffee berry disease.

The harvesting and processing of SL28 varies significantly depending on the country. Kenya operates mostly with centralised washing stations, often referred to as factories, and co-operatively owned mills. Smallholder farmers sell their coffee cherries by weight to wet mills, where the fruit is removed before the coffee is hulled and graded by size, such as AA, AB and PB, at the dry mills.

Because cherries from many different smallholders are processed together, SL28 is often mixed with other varieties such as SL34, Ruiru 11, Batian and K7.

This is quite different from the cultivation of SL28 on private estates. A private farmer might have a dedicated SL28 plot, kept separate from other variety lots. Their SL28 would then be picked, sorted, processed and packed separately from other coffees grown on the farm.

Private farmers may also use more experimental processing for their SL28 lots, whereas a Kenyan factory primarily uses washed processing for volume and consistency.

Cherries on the same branch do not ripen evenly. The best lots of SL28 require multiple passes of each tree during picking to ensure only crimson, perfectly ripe cherries are selected. Any underripe cherries are removed during the early stages of processing.

Typical Maturation Timeline

SL28 typically follows this maturation timeline:

• Year 0: Seedling germination and nursery stage
• Year 1: Root growth and branching
• Year 2: Early blossoming
• Year 3: Earliest commercially viable coffee production
• Year 4–5: Full yield potential is reached
• Year 6+: Peak production, with the best yield and cup quality
• Year 15+: Can remain productive with good pruning and management

According to World Coffee Research, some SL28 trees have been actively producing coffee for over 60 years.

Where Can I Buy SL28?

While widely available in bags of Kenyan coffee, SL28 is a little harder to come by as a single-variety lot. It is usually sold by specialty roasters that source single origin microlots.

We are currently featuring a Peru Natural SL28 from Marcos Herrera.

What Does SL28 Look Like?

SL28 cherries are medium-sized and contain medium-large, elongated beans, which are consistent in shape and size in high-quality lots.

SL28 trees are tall in stature, with a spread-out canopy. The branches are heavy, so they may droop when bearing a heavy load of cherries. Unpruned, they can grow as tall as 3 metres, although most farms maintain them at a little over 2 metres for easier harvesting and management.

SL28 vs Gesha: What’s the Difference?

SL28 and Gesha have a few similarities:

• Both were discovered partly due to their disease resilience.
• Both were widely adopted on farms due to their high cup quality.
• Both have tall plant structures.
• Both prefer to grow at high altitudes.
• Seeds were initially collected in Africa during the early 1930s.
• Both have seen competition success in the Cup of Excellence and the World Barista Championship.

However, they also have some distinct differences:

• SL28 originates from Kenya, while Gesha originates from Ethiopia.
• SL28 is more resilient to drought.
• Gesha tree branches are brittle and prone to snapping, while SL28 is sturdier.
• SL28 has a sweeter, more purple and red berry-like flavour profile with a more syrupy body. Gesha is more floral, citrusy and tea-like.
• SL28 is typically less expensive.
• Gesha is more commonly used in competitions.

The Rarity of SL28

SL28 is not too rare, unless you are looking for an isolated single-variety lot. SL28 is usually the primary variety in Kenyan coffee, with SL34, Ruiru 11 and Batian often accompanying it.

You can find SL28 as a single-variety lot from Colombia, Costa Rica, El Salvador, Guatemala and some private estates in Kenya.

Is SL28 Expensive?

SL28 is usually a little more expensive than traditional varieties, but is not likely to break the bank in the same way as a high-end Gesha might. If you are looking for juicy brews that pack a good amount of flavour, SL28 is a relatively inexpensive choice, although it tends to be a little more expensive than a classic Bourbon or Caturra.

Alternatively, if you are not determined to brew pure SL28, most bags of Kenyan coffee contain some SL28 at a more approachable price point.

How to Brew SL28

SL28 is generally not difficult to get right. It naturally has tonnes of sweetness and body with minimal bitterness, meaning most people will get a brew they are at least fairly happy with without too much difficulty.

The recipe for washed SL28 is ideal for both single-variety lots and Kenyan heirloom lots. By using a V60 and a coarser grind, we can achieve a bright, silky cup with plenty of sweetness.

In contrast, the natural SL28 approach uses a negotiated flat paper in an Orea brewer to maximise contact between the water and the grounds, increasing both sweetness and body.

Our Favourite Recipe for Washed Kenyan SL28

• Coffee: 14g, medium+ grind, around 26–28 clicks on Comandante C40
• Water: 240g, 93°C, 60–80ppm
• Dripper: V60 with Cafec Abaca cone paper, or Hario V60 paper

1. 00:00: Spiral pour 60g water
2. 00:45: Spiral pour to 120g
3. 01:20: Centre pour to 180g
4. 01:50: Centre pour to 240g
5. 02:45: Approximate drawdown time

Our Favourite Recipe for Natural SL28

• Coffee: 14g, medium grind, around 25–27 clicks on Comandante C40
• Water: 230g, 90°C, 60–80ppm
• Dripper: Orea 01 with flat paper

1. 00:00: Spiral pour 35g water
2. 00:35: Spiral pour to 120g
3. 01:20: Centre pour to 230g
4. 02:10: Approximate drawdown time

Play with ratios when brewing SL28, as it can be syrupy and sweet at tighter ratios, but can also lean into silkier, tea-like brews at lower strengths with longer brew ratios. If you would like your V60 to be a little more sweetness-forward than acidity-forward, use 40g for your first pour instead of 60g.

These are just our personal favourites, though we have plenty more recipes for you to explore on our blog. Try them out and let us know what you think.

Final Thoughts on SL28

SL28 has been a defining part of the history of specialty coffee, tracing back to early research conducted in a colonised coffee-producing region. What’s more, it has continued to define the potential of East African coffee to this day, holding its own against other high cup-quality varieties.

SL28 has been largely unaltered, but has remained a reference point for high-quality coffee for nearly a century.

Frequently Asked Questions

What is SL28 Coffee?

SL28 is a variety of coffee that was discovered, selected and distributed across Kenya around 90 years ago. It was part of an evaluation of coffee varieties conducted by Scott Agricultural Laboratories, which saw the assessment of 42 unique varieties. They were named “SL” after the lab, with a number to denote order of selection.

What Does SL28 Taste Like?

SL28 is famous for its big blackcurrant notes. Usually, the cup is sweetness-focused with bright citrus acidity and soft Assam tea-like notes. Natural processes lean into the sweetness even more, with blackberry and blackcurrant jam, and sometimes complex wine notes.

Is SL28 Fruity?

SL28 is exceptionally fruity. You can mainly expect red and purple berry notes including blackcurrant, blackberry, redcurrant, strawberry and raspberry.

What is the Origin of SL28?

It comes from a drought-resistant variety that was initially discovered in Tanzania. Seeds were brought back to Scott Agricultural Laboratories in Kenya, where pest and disease resistance, as well as cup quality, were assessed. It was named SL28 before being spread to farms around Kenya.

Where is SL28 Grown?

SL28 is most commonly found in Kenya, its birthplace. However, it has also been adopted by farmers in Latin America due to its exceptional cup quality.

Why is SL28 so Highly Regarded?

SL28 has had a reputation as a high-quality variety for nearly 90 years. It has performed excellently in Cup of Excellence competitions and was used by Dale Harris in the 2017 World Barista Championship. SL28 has a fruit-driven quality that many coffee enthusiasts love.

Is SL28 Rare?

SL28 is a little rarer than traditional Bourbon varieties. It is most commonly found in Kenyan coffee, mixed with other Kenyan varieties. SL28 becomes rarer when you look for single-variety lots.

Is SL28 Expensive?

SL28 is not usually at an unaffordable price point, and is a good option if you would like to treat yourself to a high-quality coffee at an approachable price. The premium price often comes with isolated SL28 lots. Kenyan coffees are usually a little more affordable, but are rarely pure SL28.

How Should I Brew SL28?

SL28 is not a particularly fussy coffee, and there are plenty of ways to brew it. It has low bitterness, balanced acidity and plenty of sweetness, so you are likely to get an enjoyable cup regardless of how you brew. Brewing with a V60 brings out more vibrancy, juiciness and tea-like qualities, whereas a flat bottom brewer can emphasise sweetness and body.

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About the Author

Gage is a competition barista and was previously Head of Coffee for Sale Moon Coffee. He has spent a long time working with Harmony Coffee. He is a barista trainer, has trained many baristas, and has competed in countless coffee championships.