The two main species of coffee plants are Arabica coffee and Robusta coffee. Robusta tends to be more bitter than Arabica, and is generally considered to be a lower quality coffee. This is not to say that there is anything bad about Robusta. The "lower quality" stigma is primarily an artifact of its being easier to grow, and hence cheaper. Undeniably, it tends to be a little bitter, and is generally not used for espresso blends. But sometimes some Robusta is added to an espresso blend to give it a little more strength and character.
Robusta is primarily used for regular coffee and instant coffee. Another contrast with Arabica is that Robusta has a higher caffein content than Arabica. As we mentioned, the generally preferred Arabica coffee is more difficult to grow than Robusta, since the coffee plants require a very tropical climate and high altitude. Nonetheless, Arabica accounts for 75-80% of the world's coffee production.
There are two optimal growing climates for Arabica coffee: subtropical regions in the 16-24 degree latitude range, and equatorial regions with latitudes less than 10 degrees. Arabica coffee thrives best in volcanic soil. At higher elevations, Arabica grows more slowly, producing a more aromatic coffee. Conversely, Robusta coffee is generally grown at lower altitudes since it is more tolerant to warm conditions than Arabica coffee; indeed its name denotes the robustness of the Robusta coffee plant.
To propogate coffee plants from coffee beans, the ripe coffee cherries - containing the coffee beans - are collected, and the mucilage is removed via fermentation. The coffee beans (seeds) can be planted immediately, or dried for later use.
Coffee seeds are best germinated in a sand bed covered with moist burlap or straw, or in polybags filled with manure and topsoil, gravel and course sand, coffee husks and coffee pulp, and a good dose of nitrogen fertilizer. When the radicals emerge, the coffee seedlings are removed, and then planted in coffee nursery beds.
To plant the coffee seedlings, the coffee nursery bed should be enriched with cow manure and phosphate fertilizer. Coffee seedlings should be spaced at 4-8 inch intervals so as to have enough space to grow. Initially, coffee nursery beds should be semi-shaded. Shading should be removed slowly, leaving the coffee plants completely unshaded for the last two months prior to the final planting of the coffee plants. The coffee plants are ready for transplanting to a coffee field when they reach 8-16 inches in height..
On final planting in the coffee field, the coffee plants should be spaced at 16 inch intervals, and should be fertilized with potassium, phosphorus pentoxide, dolomitic limestone, copper, boron, and zinc. After the coffee plants start growing, periodic applications of nitrogen should be applied 4-6 inches from the trunk. The amount of fertilizer needed depends on the age of the coffee plants.
Coffee is actually a fruit. Coffee plants form white coffee blossoms that are short-lived (a day or so). After this, round coffee "cherries" form. It takes 3-5 years for the coffee plant to produce the coffee fruit, which will only happen if the coffee plant is grown in the right climate.
Before ripened, the coffee cherries are green. When the coffee cherries become red and glossy, it is time to harvest the coffee. Coffee harvesting can be done by hand, or by machine. To maximize the coffee harvest, hand picking of the coffee is recommended, since any unripened coffee cherries can be left to ripen before harvesting later. When harvesting by machine, a portion of the harvested coffee crop will not be ripe. For example, in Brazil, coffee crops are harvested when 75% of the coffee crop is ripe.
It takes 5-8 pounds of harvested coffee cherries to eventually yield 1 pound of high-quality coffee beans.
...written by your friends at The Coffee Brewers