The Coffee Plant

The coffee plant belongs to the Rubiaceae family and is an evergreen woody perennial. Two main species of the coffee plant are cultivated today, Coffea arabica and Coffea canephora. Coffea arabica, commonly known as Arabica coffee, accounts for 75-80% of the world's production. Coffea canephora, known as Robusta coffee, is a more resilient plant than the Arabica shrubs, but produces an inferior tasting beverage. The coffee plant can grow to heights of 10 meters if not pruned, but producing countries maintain coffee at three meters to ease picking. Each hectare of coffee produces 86 lbs of oxygen per day, which is about half the production of the same area in a rain forest.

In the axils of the leaves sweetly smelling flowers grow in clusters within three to four years after the coffee is planted. The plan produces fruit only in the new tissue. The Arabica species is self-pollinating, whereas the Robusta species depends on cross pollination. When flowers are fertilized, within 6 to 8 weeks cell division occurs and the fruit remains as a pin head for a period that is dependent upon the growing climate. The the flower ovaries will then develop into what is known as drupes in a rapid growth period. The growth period will take about 15 weeks after flowering. During this time of growth the integument takes on the shape of the final coffee bean. After the completion of the rapid growth period the integument and parchment will be fully grown and not increase in size. The endosperm remains small until about 12 weeks after flowering. At this point in time the endosperm will suppress, consume, and replace the integument. The remnants of the integument are what make up the silverskin. The endosperm will completely fill the cavity made by the integument nineteen weeks after flowing. The endosperm is now white and moist, but will gain dry matter during the next several months. During this time the endosperm attracts more than seventy percent of the total photosynthesates produced by the tree. The mesocarps will expand to form the sweet pulp that surrounds the bean. The cherry will change color from green to red in about thirty to thirty-five weeks after flowing.

The root system on a coffee bush can extend as much as 20 to 25 kilometers in total length and the absorbing surface of a tree ranges from 400 to 500 square meters. On a coffee plant there are main vertical roots, tap roots, and lateral roots which grow parallel to the ground. Tap roots will extend no further than 30-45 centimeters below the soil surface. Four to eight axial roots may be encountered which often originate horizontally but point downward. Lateral roots can extend 2 meters from the trunk of the coffee plant. 80 to 90% of the feeder root is in the first 20 centimeters of soil and is 60-90 centimeters away from the trunk of the coffee tree. The greatest root concentration is 30 to 60 centimeters deep. The root systems are heavily affected by the type of soil and the mineral content of the soil. To be thick and strong the root system needs an extensive supply of nitrogen, calcium and magnesium.

The elliptical leaves of the coffee tree are shiny, dark green, and waxy. Incidentally, the coffee plant has become a major source of oxygen in much of the world.