Class of the coffee plant: Dicotyledoneae
Subclass of the coffee plant: Sympetalae or Metachlamydeae
Order of the coffee plant: Rubiales
Family of the coffee plant: Rubiaceae
Genus of the coffee plant: Coffea
Some Species of the coffee plant: Coffea Arabica, Coffea Robusta
The genus, Coffea, which the common coffee tree belongs, contains about 25 species. Coffea Arabica is the largest cultivated coffea but other commercially known are Coffea Liberica, Coffea Stenophylla, Coffea Excelsa, and Coffea Canephora (Robusta). By far, Coffea Arabica and Coffea Robusta are the species of coffee plant most commonly cultivated. The other sspecies of coffee plants are not cultivated commercially. There are indoor coffee plants grown for esthetics because the plant can do well indoors where it is carefully cared for.
The coffee plant originally grew in African tropical forests. Some varieties of coffee plant typically grow over 30 feet. But, in cultivation, for ease of picking of the coffee berry, the coffee tree is seldom allowed over 15 feet. The Arabica coffee plant is typically smaller than the Robusta coffee plant.
Coffea Robusta is a shrub type plant. The Robusta coffee plant grows similar to a bush, in that it has several trunks. Although, the coffee plant may have one trunk, it tends to have more. Additionally, this characteristic of trunking is different among the various coffee species.
Coffea Arabica is a tree type plant. The Arabica coffee plant drives a straight up trunk with branches paired off outward and lower branches tend to droop downward.
Coffee Leaf Kind: abrupilypinnate. It is a bipolar leaf structure, where two leafs grow from the stem opposite each other. The distance between leaf pairs an the stem is about 1 to 3 inches. The leaf pairs generally are at 90 degree rotation for each pair on the stem. It is an evergreen.
Coffee Leaf Margin: entire - undulate. The edges of the leaf have a ripply look to them. However, younger plants have an even edge look to them. This varies among types.
Coffee Leaf Shape: oblong - ovate. Typically, the plant types are more ovate than oblong. This varies among types.
Coffee Leaf Base: acuminate. This characteristic is fairly common among types.
Coffee Leaf Tip: acuminate. This also is pretty much common among types.
Coffee Leaf Venation: midrib to margin. This varies among types.
Front view of a typical coffee leaf
Back view of a typical coffee leaf.
Typical coffee leaf lengths: 4 to 6 inches.
Typical coffee leaf widths: 1 to 3 inches.
Coffee leaf color: is a deep green with a waxy surface.
The coffee plant flower is white, are produced in dense clusters, and formed in the axils of the leaves. (Where the leaf protrudes from the stem.)
The coffee plant flowers have five-toothed calyx (outer wall of the flower), a
tubular five-parted corolla (inner wall of the flower).
Five stamens (pollen bearing organ) and a single bifid style (one piece pointed and divided in two equal parts). The coffee plant's flowers last only a few days. The coffee plant blooms shortly after a rain. The coffee flower has a strong pleasing smell. Also the flower is different for each coffee plant type.
Sexually, the Coffea arabica is autogamous, in that it can pollinate itself, where as the Coffea Robusta can not pollinate itself.
After pollination of the coffee plant, a small green coffee berry appears called a drupe. This coffee berry grows to about 15-35 millimeters (0.5 inch to 1.25 inches) depending on species. The coffee berry grows in clusters.
When the coffee berry is ripe it turns red. At maturity, the coffee berry is bright red. After what is considered ripe, the coffee berry turns brown to reddish brown and falls off the coffee tree. Many coffee growers allow the berry to fall to the ground, but most pick it when it is red.
There are typically two seeds per coffee berry packed with the flat end facing each other, but that is not always the case. A special case which is common is called peaberry which is a single seed. But, there can be more than two in a coffee berry also.
The outer skin of the coffee berry is generally tough and can withstand handling. The inner pulp of the coffee berry is generally mushy. In a few types of coffee plants, the pulp is more valuable than the bean itself. This is because the coffee berry pulp has a high sugar content and can be fermented making a coffee liquor or a tea made from the pulp. The coffee berry parchment shell is fairly tough. This is taken off in the last coffee bean processing stage. However, the coffee silverskin is so thin and attached so well it tends to stay with the coffee bean right up to roasting. When roasted, the silverskin can, and usually does, crack off the coffee bean. The silverskin cracks off because it does not expand like the inner coffee bean does when roasted. This posses a problem in two ways. First it is a thin messy chaff which is undesirable and must be removed from the batch of roasted coffee beans for cosmetic reasons. Second, it can easily catch fire.
Cultivation of the coffee plant over a period of several hundred years has brought about considerable variations to grow in various types of climate and soil conditions. The color and chemical content of the "green bean" typically reflects these different types of the coffee plants.
Typically, the geography of the coffee plant is in a tropical 25 degree latitude belt on both sides of the equator. The Arabica coffee plant grows best at altitudes between 3000 and 6000 feet. Coffee plants can be grown at lower altitude but attack from various parasites cause problems which make low altitude cultivation hard.
Desirable temperature averages between 65 to 75 degrees Fahrenheit. The Arabica coffee plant will grow in hotter areas but is not well suited for higher temperature. The Robusta coffee plant is typically located in hotter and more humid areas at lower altitudes around 600 to 1500 feet. Frost will kill every variety of coffee plant known. Thus, it limits the altitude and latitude at which this plant can thrive. The coffee plant is susceptible to changes in temperature. Temperature affects the color of the coffee leaf, the hotter the lighter the color green. The longer periods of deep green, the healthier the coffee plant.
Generally, the coffee growing area takes at least 75 inches of rain fall per year. The rainfall should be spread over a 9 month period, with about 2-3 months of only a few inches of rain. The dry spell is needed to allow coffee buds, flowering, and new growth. Erosion aside, the coffee plant will grow well with much more water so long as it does not sit in water. In areas with less than 75 inches per year, careful irrigation can provide adequate water for the coffee plant.
The soil where a coffee plant grows should be humus, generally porous, and a slight tendency toward acid but more or less a neutral pH. Coffee plants can grow in slightly alkaline soil. But too much acid or alkaline will kill the coffee plant. Additionally, there is a preference for pH which depends on the type of coffee plant. Mulching the surface with grass, compost, or vegetable refuse is common ways to help facilitate growth of the coffee plant. Preferably coffee plant soil is heavy to work and not too loose and sandy. Very generally speaking, the planting conditions of the coffee plant are similar as for a camellia. The coffee plant doesn't like hard pack soil or sitting in water for long periods of time. The coffee plant's subsoil should stay moist but not soggy as to promote rot. The coffee plant's roots breath and actually need some air. Thus, constant watering of the coffee plant, or the coffee plant sitting in water, causes the leaves to turn yellow, young shoots wilt, and the coffee tree dies.
The coffee plant likes high humidity of about 90 percent. The humidity in the air performs two functions for the coffee plant, one is to keep evaporation from the coffee plant at a minimum, the other is to diffuse the light striking the coffee plant.
Coffee plants like filtered to moderate sun light. Coffee grows on sides of mountains which makes for natural partial lighting conditions. However, some types of coffee plants can take direct sun light without overhead shade trees or a mountain side cutting off a half days light. And again, this differs with coffee plant types. There are four kinds of shade; temporary, permanent, forest, and soil shade. Bare soil loses its richness and character by being baked by the sun and beat on by the rain. If the sun bakes the top soil too much, the coffee plant's roots die. Therefore, for most coffee plants, the soil should be shaded as much as possible. Both mulch and the way the coffee plant is cropped accomplish this task. In some places cover crops as Leucaena glauca are planted between the coffee trees to keep the soil in good shape. Depending on plant, the leaves may need shade too. The coffee plant generally requires some direct sun light for a portion of the day, so total permanent shade is not a good practice. Forest shade has a problem with the type of plants surrounding the coffee tree. The wrong type of forest plants can take nutrients from the soil or actually strangle the coffee plant.
The coffee plant does not do well in high wind either. Wind dries the leaves out quickly. Consequently, the drying effect, quick temperature changes, and the transportation of unwanted seeds makes windy conditions undesirable for coffee growing.
Typically, the coffee plant can produce berries for about 60 years but most commercial coffee operations limit the life of the coffee plant to about 20 years. Some coffee growers feel earlier termination is appropriate. Although the coffee tree produces berries at the age of 3, it starts producing at about 5 years old.
The two basic propagation methods both work with the coffee plant, grown from seeds, or cloned from cuttings. Seeds take about 5 to 6 weeks to germinate. Tender shoots require more shade. Generally, the cuttings, or seedlings are nurtured in a nursery before being planted in the field. A general rule of thumb is plant the seedling when it has more than four and less than eight branch pairs, which tends to be 5 to 6 months. Coffee plants can be grafted. Grafting tends to adapt a plant for growing conditions and disease resistance, although it is not a common practice. It should be noted that the coffee seed will not remain fertile for long periods of time. Due to the pulpy nature of the berry, the seed either starts to germinate when it is removed from the tree or it ferments and rots.
Coffee growers refer to pruning as training. Exactly how the coffee plant is trained depends on the type of coffee plant, the environment, and the labor. The coffee plant branches can become so heavy with berries that they break, so it is important to train the coffee plant such that it is strong enough. From time to time, the coffee plant gets too large of root system for the soil conditions or the middle lateral branches become damaged, so the coffee plant is trunked. Trunking the coffee plant is cutting it way back, right down to where only two branches near the bottom are left on it.
COFFEE PLANT DISEASES
The coffee plant is very prone to sever weather conditions, diseases and attack from parasites. The Robusta plant being better adapted to resist such attacks which is how it got it's name "Robust." The Mediterranean fruit fly is a serious problem. The stephanodores leaf-miner is referred to as the coffee-plague. The Hemileia Vastatrix, leaf rust fungus, can easily wipe out a plantation, and has destroyed the whole know world's crops in the past. This is a serious disease.
A note from one who is not a botanist. Plants do not take their nutrients from the soil. No plant takes it's nutrients from the soil. Plants get their nutrients from the fungus in the soil. Thus, although the plant looks as though it is getting it's nutrients from fertilization, it actually is not. The fungus is getting it's food from fertilization and the plant is getting it's food from the fungus. Interesting!