Excelsa Coffee: The Case for Its Recognition as an Independent Coffee Species
For decades, Excelsa coffee has lived in the shadow of its botanical relatives, often grouped within the Coffea liberica species despite its unique genetic, morphological, and agricultural attributes. However, mounting scientific evidence suggests that Excelsa coffee should be recognized as an independent coffee species, separate from Coffea liberica, Coffea arabica, and Coffea canephora (commonly known as Robusta).
In this article, we present a compelling argument—based on genetics, plant morphology, biochemical composition, and agricultural significance—that Excelsa coffee is not merely a variety of Coffea liberica but a distinct species in its own right. We also provide a comparative analysis of the four main coffee species and their unique attributes.
A Brief History of Excelsa Coffee Classification
Excelsa coffee (Coffea excelsa) was first documented in 1903 by a botanist named Auguste Chevalier, who initially classified it under Coffea liberica var. dewevrei, a subcategory of Liberica coffee. This classification persisted for over a century, mainly due to superficial similarities between Excelsa and Liberica trees, such as their tall growth habits and large leaves.
However, modern advancements in genetic analysis, biochemical profiling, and sensory evaluation have revealed significant differences that warrant Excelsa’s classification as a separate species.
1. Genetic Evidence: Distinct DNA Composition
Recent genomic studies have demonstrated that Excelsa coffee possesses unique genetic markers that differentiate it from Coffea liberica. While both species share some similarities in their chromosomal structure, Excelsa exhibits distinct DNA sequences that place it in an evolutionary lineage separate from both Liberica and Robusta.
- ● Genetic Distance Analysis: DNA sequencing studies have identified significant genetic divergence between Excelsa and Liberica, suggesting that Excelsa evolved independently from a common ancestor rather than being a mere variant of Liberica.
- ● Chromosomal Differences: While Arabica coffee has 44 chromosomes and Robusta has 22, Excelsa, like Liberica, has 44. However, within this chromosomal structure,
Excelsa has unique gene expressions related to drought tolerance, disease resistance,
and biochemical composition that set it apart.
● Distinct Reproductive Patterns: Unlike Liberica, Excelsa demonstrates a different
flowering and pollination cycle, suggesting a genetic adaptation to different environmental conditions.
2. Morphological Differences: A Unique Plant Structure
Excelsa coffee is often confused with Liberica due to some overlapping physical characteristics, but a closer examination reveals several key morphological differences:
● Leaf Shape and Size: Excelsa leaves are narrower and more elongated than the broader, more rounded leaves of Liberica.
● Tree Growth and Branching: Excelsa trees have a more compact growth habit compared to the towering, irregular structure of Liberica.
● Root System: Excelsa’s root system is shallower and better adapted to loamy and sandy soils, while Liberica prefers deeper, more clay-rich soils.
● Cherry and Bean Shape: Excelsa coffee cherries are more oval and symmetrical than the asymmetrical, teardrop-like cherries of Liberica. The beans themselves are also smaller and denser than those of Liberica.
3. Biochemical Composition: Unique Flavor and Caffeine Content
Excelsa coffee exhibits a biochemical profile distinct from all other coffee species, particularly in terms of caffeine content, sugar composition, and volatile compounds responsible for flavor and aroma.
● Caffeine Content: Excelsa coffee has a lower caffeine content (0.86–1.13%) than both Arabica (1.2–1.5%) and Robusta (2.2–2.7%), making it a desirable option for consumers seeking a less caffeinated but flavorful coffee.
● Acidity and Flavor Complexity: Excelsa coffee is known for its fruity, tart acidity, which is much more pronounced than in Liberica coffee. It also has a more complex profile with woody, floral, and dark fruit notes, distinguishing it from the earthy bitterness of Robusta or the smoother, chocolatey notes of Arabica.
● Sugar and Lipid Composition: Excelsa contains a unique balance of sugars and lipids that contribute to its rich body and aromatic complexity. Unlike Robusta, which has a high bitterness due to its chlorogenic acid content, Excelsa offers a pleasant sweetness with a balanced acidity.
Agricultural and Environmental Adaptability
Excelsa coffee demonstrates remarkable resilience to environmental stressors, making it an ideal crop for sustainable coffee production.
● Drought and Heat Resistance: Excelsa trees can thrive in temperatures exceeding 35°C (95°F), making them highly suitable for cultivation in regions affected by climate change.
● Pest and Disease Resistance: Unlike Arabica, which is highly susceptible to coffee leaf rust and berry borer, Excelsa has a natural resistance to many common coffee pests and diseases. This trait reduces the need for chemical pesticides, making Excelsa a more sustainable option.
● Shade Tolerance and Agroforestry Integration: Excelsa thrives in agroforestry systems, where it can be intercropped with other plants, improving biodiversity and soil health. The Four Main Coffee Species: A Comparative Analysis There are four primary species of coffee grown commercially, each with distinct attributes:
| Characteristic | Arabica (Coffea arabica) | Robusta (Coffea canephora) | Liberica (Coffea liberica) | Excelsa (Coffea excelsa) |
|---|
| Caffeine Content | 1.2–1.5% | 2.2–2.7% | 1.5–1.8% | 0.86–1.13% |
| Flavor Profile | Smooth, mild acidity, floral and fruity notes | Bitter, earthy, woody | Smoky, nutty, woody | Fruity, tart, complex, dark fruit and floral notes |
| Bean Shape | Small, oval | Small, round | Large, asymmetrical | Medium, oval, symmetrical |
| Climate Preference | Cool, high-altitude | Warm, low-altitude | Hot, humid | Hot, drought-resistant |
| Pest/Disease Resistance | Low | High | High | High |
| Primary Growing Regions | Latin America, Africa, Asia | Africa, Vietnam, Indonesia | Philippines, Malaysia, West Africa | Southeast Asia, Central Africa |
Conclusion: The Case for Excelsa as an Independent Coffee Species
The evidence overwhelmingly supports the classification of Excelsa coffee as a distinct species rather than a variant of Liberica. Its unique genetic structure, morphological characteristics, biochemical composition, and agricultural adaptability distinguish it from all other coffee species.
Recognizing Excelsa as an independent species is not just a matter of botanical accuracy—it has profound implications for the coffee industry. It allows farmers to cultivate and market Excelsa with clearer differentiation, opening up new opportunities for specialty coffee markets. Moreover, as climate change threatens traditional coffee-growing regions, Excelsa’s resilience offers a sustainable alternative for future coffee production.
It is time for the international coffee community, including the World Coffee Research organization and botanical taxonomists, to acknowledge Excelsa coffee as what it truly is: a unique, independent species that deserves its rightful place in the coffee lexicon.
Excelsa is not Liberica. Excelsa is Coffea excelsa.