Arabica and robusta dominate the global coffee market, making up almost 100% of all coffee sold across the world. Despite this, however, there are 122 other known species within the Coffea genus, yet these have little impact on the wider industry.

However, with 60% of all coffee species under threat thanks to deforestation and the impact of climate change, some are looking at these other, unknown species to provide the industry with more security.

One of these other, lesser-known species is Coffea stenophylla, otherwise known as the “highland coffee”, which originates from the hills of Sierra Leone and neighbouring countries.

Little is known about stenophylla; however, we spoke to two researchers about its history and its potential to support the global coffee market going forward. Read on to find out what they said.

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The Origins And History Of Stenophylla

Stenophylla was first formally identified in the 19th century, several hundreds of years after people had started trading arabica and robusta. 

Jeremy Haggar is a Professor of Agroecology at the University of Greenwich in London. He says: “C. stenophylla was scientifically described in 1834… it was cultivated in Sierra Leone at that time.”

“There are reports from the Royal Botanic Gardens, Kew, and the British authorities in Freetown, Sierra Leone, that C. stenophylla was cultivated and exported from Sierra Leone up to the 1890s,” he adds. “There are also reports that it was also cultivated in Guinea into the early 1900s.”

Aaron Davis is the Head of Coffee Research at the Royal Botanic Gardens, Kew. He co-wrote Lost and Found: Coffea stenophylla and C. affinis, the Forgotten Coffee Crop Species of West Africa with Jeremy.

In the paper, he notes that stenophylla was cultivated at scale in the late 19th century in both Guinea and Sierra Leone. From there, the crop was largely exported to France.

At the time, French exporters paid high prices for stenophylla; locals that drank the species in Sierra Leone reported a favourable taste profile, while the Royal Botanic Gardens pointed out that the species had the potential to compete with arabica.

Eventually, stenophylla made its way along the west coast of Africa and soon started appearing on the east coast, too. “It was also cultivated in Ghana, Senegal (where it was known as Senegal coffee), [the] Ivory Coast, possibly through early intervention by the Portuguese, and in Uganda,” Aaron writes.

However, despite this popularity, stenophylla came to be at a disadvantage as time went by. The plant can take more time to fully mature when compared to arabica and robusta, and is less productive.

Natural competition in the coffee market is most likely why the species was forgotten, Jeremy tells me.

“After [the late 19th century], its cultivation declined, but we assume this was due to the introduction of robusta coffee by the colonial authorities, which is a more productive species.”

Plant Characteristics And Growing Conditions

In their research visits to Sierra Leone between 2017 and 2019, Aaron and Jeremy travelled across the country to track stenophylla in the wild and on farms.

Initial fieldwork was unsuccessful, and they soon became aware that they were dealing with a very rare plant. The last official sighting of stenophylla in Sierra Leone was in 1954.

In 2019, Aaron and his colleagues at Kew formally listed this species as threatened with extinction in the wild. 

The paper notes that in late 2019 at the Kasewe Forest Reserve, Moyamba District, they found a “single sterile (no flowers or fruits) immature plant”, while they located “a small population (with mature trees up to seven metres tall) matching [the] species in the forested area of Kambui Hills”.

The stenophylla plant grows between 200 and 700 m.a.s.l., and its growth cycle is closely linked to rainfall in the area. During drier seasons, stenophylla enters a state of near-dormancy, until rainfall stimulates flowering and vegetative growth resumes.

Its star-shaped flowers have seven to nine white, petal-like lobes (arabica and robusta usually have five lobes), and its leaves are distinctive, as Jeremy explains. “One of the common names for C. stenophylla is ‘narrow-leaved coffee’,” he says. “[This is because one] of its distinguishing features is narrow leaves with long-pointed tips.

“Another distinguishing characteristic is that the fruits are black when ripe,” he adds, which is a useful feature for identifying stenophylla plants in the wild.

The fruit of the stenophylla plant grows very slowly for six to eight weeks. After this, they then grow in size very quickly, and their water content can increase by as much 85%. The seeds within the fruit take another 30 to 35 weeks to fully mature.

However, stenophylla plants may have greater resistance to drought than the other main coffee crop species, as indicated by the growing conditions where the plant has been found naturally in other regions of West Africa.

“In Ivory Coast (at Ira Forest), C. stenophylla occurs on the upper, drier parts of hills,” Aaron writes. “In the same location, C. canephora and C. liberica were found in the valleys (i.e., the lower, wetter areas).

“The locations for this species in Ivory Coast are generally drier than [in] Sierra Leone, with rainfall in the region of 1,500–1,700mm per year, a 3–4 months dry season, and an average annual temperature of 25.5°C.”

Stenophylla Today

Apart from a few plants in research collections, Coffea stenophylla is not farmed or otherwise cultivated today. Aaron writes: “The export of C. stenophylla in Sierra Leone and Guinea amounted to around three to five tonnes (3,000 to 5,000kg) per year, although this does not include the amount of coffee consumed in these producing countries, which may have been substantial.

“Coffea stenophylla appears to have been a prominent feature of agriculture in Sierra Leone up until at least the 1920s, but it may have been in decline after that time, perhaps due to a fall in coffee prices,” he adds. The very last reports of its cultivation in West Africa date from the 1980s, when rare sightings were made of small-scale cultivation close to houses.

Today, Sierra Leone has just a 0.04% share of the global coffee market, but their production comes solely from robusta and liberica coffee.

Before civil war broke out in the country in 1991, it produced some 25,000 tonnes of coffee per year. Today, that number is less than 10% of what it once was just 30 years ago – around 2,000 tonnes per annum.

Throughout the 20th century as production declined, stenophylla was mostly used for research purposes. However, Aaron notes that little is still known about the species, and in particular its agronomic performance and sensory characteristics.

“C. stenophylla has not undergone sensory or agronomic evaluation in a contemporary setting,” he writes. “Despite the shortfall in our understanding of these species, the available evidence… is more than sufficient to warrant further research.” 

Historical reports from claim that stenophylla’s flavour is high-quality. More recent, anecdotal sources claim that the species has a mild taste with a tea-like texture when brewed. 

Today, most of the available seeds found in Sierra Leone have been used to breed this species in an attempt to safeguard and reintroduce it. Aaron and Jeremy tell me that this is work that they hope to develop over the coming years with partners in Sierra Leone.

Is The Species Economically Viable To Grow?

Only 36% of arable land is under cultivation in Sierra Leone, but the country’s agriculture sector employs 68% of the total population. Even so, mature forests are estimated to cover only 5% of the country. Most coffee farms are in desperate need of regeneration, and the civil war has displaced many farmers and their families.

Beyond this, there is also a lack of suitable infrastructure for coffee production, and farmers are regularly paid less than US $1 per kilogram. This means there’s little incentive for farmers to grow any species of coffee, let alone a species that most people don’t know about.

“There are currently no incentives for farmers to grow this species,” Jeremy says. “However, it is very early days in ensuring this species has the economic potential we hope for.”

A Sierra Leonean colleague of Jeremy and Aaron, Daniel Sarmu, has attempted to raise awareness about stenophylla among farmers, particularly focusing on its visual differences as compared to other species.

“50 A4 posters showing the most obvious morphological differences (leaf shape and size) between… robusta coffee, liberica and C. stenophylla were printed and distributed to district agriculture offices with coffee farming communities in southern Sierra Leone, between Freetown and Kenema,” Aaron writes. “The aim was to provide an additional means of identifying farms that might be cultivating C. stenophylla. 

“In December 2018, we followed up on the poster survey, by visiting five farms that had reported growing stenophylla.

“They all turned out to be robusta.”

Jeremy explains to me that determining the profitability for any new coffee crop species is a long, arduous process. “As a perennial crop, it will probably take five or more years to plant the first trial plantations and bring them to production,” he explains.

“[After that], we can begin to evaluate it agronomically and determine how profitable it might be for farmers to produce this species.”

Does Stenophylla Have Potential For The Wider Market?

Research conducted by Aaron and his colleagues at the Royal Botanic Gardens, Kew since 2012, has concluded that in the decades that follow, arabica plants will be impossible to grow in many areas. If we want to see the coffee industry thrive in the future, it’s important to look at and learn from other coffee species to adapt to climate change.

Stenophylla could be part of the solution in response to drastically changing climates along the Bean Belt. Aaron and Jeremy’s paper notes that “C. stenophylla is reported to withstand dry conditions, and that there may also be some resilience to high temperatures and low rainfall, compared to the main crop species”.

However, they also note that there are issues regarding the survival of this species in the wild. “In the Kasewe Hills… we were only able to locate a single plant, in an area of high deforestation,” Aaron writes.

“In the Kambui Hills… we located a small population, the extent of which is as yet unknown, but there are ongoing threats from logging, human encroachment, and artisanal gold mining.”

Aaron and Jeremy’s paper also confirms the existence of a hybrid between stenophylla and liberica, and note that this plant is of additional interest as it is exceptionally robust.

Jeremy acknowledges that thanks to the specialty coffee sector’s appreciation of exclusivity and rarity in coffee, there is potential for the species among more adventurous roasters and cafés. 

“With high interest in the potential for superior sensory qualities, there has been considerable interest in C. stenophylla from buyers to obtain samples of this coffee,” he says. 

As a result of the impact of climate change on coffee producers and their communities, researchers around the world are turning to new and innovative research programs to mitigate the impact of changing temperatures and environments.

Naturally, researchers and agronomists have also expressed interest in lesser-known, more resilient species of the Coffea genus, such as stenophylla.

Even if these species are not broadly adopted by coffee producers, the potential to create cross-species hybrids is incredibly exciting at a time where climate change is a very real threat.

Enjoyed this? Then read Exploring Ethiopian Heirloom Coffee Varieties

Photo credits: Jeremy Haggar, Aaron Davis, Daniel Sarmu

Many thanks to Aaron Davis and Jeremy Haggar for providing their expertise to this article. For more information on the C. stenophylla species, you can read their paper here.

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