The coffee plant is a shrub-like tree belonging to the Rubiaceae, Coffea genus.
Scores of species of the Coffea genus have been classified but only two have any real economic significance: the Coffea Arabica and the Coffea Canephora (Robusta).
In the wild state the coffee plant can reach a height of 8-9 metres, but in the plantations it is kept at a height of 2-3 metres for easy harvesting. The leaves are 10-15cm long and are oval-shaped or lanceolate.
The flowers are white, grow in clusters and are about 2cm. in diameter. Their life span is short (a few days) and they give off a very pleasant fragrance.
The fruit is called drupe or cherry and becomes bright red when ripe. The external layer, called the exocarp, covers the mesocarp (soft sweet pulp), inside this there are 2 seeds (endocarp) covered with a whitish film (parchment). Underneath the parchment there is another thin film, adherent to the seed (silverskin). The seeds or beans are oblong, with one rounded side and one flat side with a deep furrow; they are about 10mm long and weigh about 0.15gr.
The Arabica plant is more widespread than the Robusta (about 3/4 of the production worldwide). It differs in the colour of the leaves, the flowers and the shape, as well as in the height it reaches, 6-8 metres when not pruned. The Robusta plant, instead, can grow as high as 8-10 metres. The bean of the Arabica is flatter and longer than the Robusta, the furrow is curved and the colour green. The Robusta bean is rounder, pale green and the furrow is straight.
Robusta contains more caffeine (2-4.5 %) than Arabica (1.1-1.7%). In the cup Arabica is sweeter and more aromatic than Robusta.