Growing Coffee

The coffee plant is a tropical tree grown entirely in the tropical zones between the Tropic of Capricorn and the Tropic of Cancer. The particular variety of coffee will determine the type of climate and soil it will need and the elevation and shade required. The highest quality coffees come from the Coffea arabica species usually grown in the shade at high altitude. There are many varieties of arabica coffee with only a few producing top quality coffees. The Coffea canephora or robusta species is a low quality coffee grown near sea level and used mainly as filler coffee in blends to reduce cost. The arabica species grows best where the rainy and dry seasons are well defined, and the altitude is between 3000-6000 feet. These conditions result in one coffee growing season and one maturation season, preferably in the coldest part of autumn. Where the rainy and dry season is not as well defined the coffee plant may have ripe fruit, green fruit and be in the flowering stage at the same time. Growing regions with this type of climate will usually have two harvest seasons each year.

Three to four years after the coffee tree is planted the plant will form flowers that will last only a few days. Flowering only occurs in new growth. The Coffea arabica plant is self-pollinating and about 6-8 weeks after each coffee flower is fertilized cell division occurs and the coffee fruit remains as a pin head for a period of up to 6 weeks. The pin head will then develop into the cherry fruit in a rapid growth period that occurs about 15 weeks after flowering. During this time the integument takes on the shape of the final coffee bean. After the rapid growth period the integument and parchment are fully grown and will not increase in size. This period of growth will determine the size of the coffee bean.

The endosperm remains small until about 12 weeks after flowering. At this time it will suppress, consume, and replace the integument forming the coffee bean. The remnants of the integument are what make up the silver skin that covers the mature bean. The endosperm will have completely filled 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 consumes more than seventy percent of the total energy produced by the tree and stunts the tree growth. The mesocarp will expand to form the sweet pulp that surrounds the coffee bean. The coffee cherry will begin to change color from green to yellow to red about thirty to thirty-five weeks after flowering and is ready for harvest.

The coffee tree is usually replaced within 15 to 20 years of it's first planting to keep yields high. Pruning is usually done as needed or for some regions the tree is pruned heavily every 4 to 5 years for the same reason. Pruning also keeps the plant at a manageable height to make harvesting all the cherries possible. In Ethiopia though, where the Coffea arabica species is believed to originate, coffee is still harvested in the wild from non-commercial coffee plants.

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