Most Arabica coffee trees in cultivation around the world are no more than three or four generations from the wild. What this means is that many features of coffee’s physiology resemble the phenotypes of the Ethiopian landrace varieties from the wild forests. That means they still favor the types of environment found in the cool understory of the wild forests which historically have experienced a winter dry season.
Selected sun adapter cultivars under intensive management conditions have allowed arabica coffee plantations to be spread to marginal regions with average temperatures as high as 24–25ºC, such as in northeastern Brazil On the other hand, in regions with a mean annual temperature below 17–18ºC, growth is largely depressed.
The optimum terroir for arabica coffee is relatively confined to areas that resemble the terroir of the wild forest of Ethiopia and in the same way the anatomy of coffee around the world remain quite similar to landraces from the cloud forests of South Sudan’s Boma plateau and the Ethiopian highlands. First part is the lives the leaves of coffee plants are shiny and usually dark green in color. The leaves have ruffled edges that look like edges of a Kalita wave filter paper. The leaves are usually located in pairs along straight branches. Plants tend to shed leaves by the end of the dry season coinciding with the harvesting period. The leaves of coffee plants don’t react very well to wind stress. High winds can lead to a reduction of leaf area and a shortening of the internode length of the branches. Mature leaves will often reach around 15cm in length. After that the root system of an arabica coffee tree is concentrated in the first 30 cm of soil. It is distributed in a circle of approximately 1.50 m in diameter around the trunk. Unless trained in a special way, most Arabica plants are single trunked. Plants that are multi-trunked have either been stumped to encourage regrowth or pegged down as young saplings to encourage suckers (new potential trunks) to grow up. This is a common practice in Kenya and Uganda.
On a branch of a coffee plant, the leaves are arranged in pairs spaced along each branch with a few CMS between them. The meeting point of each pair of leaves is called the axil. It is between the pairs of leaves at the axil that the coffee flowers appear. Unlike most flowering plants, the flower buds occur in clusters of as many as 16 flowers. This is called an inflorescence (a cluster of flowers on one branch). Each flower has five petals which come together in the center to form a funnel-like tube. The calyx is very rudimentary, being five-denticulate, and the corolla is white, the five petals being united in a tube to form a salver-shaped corolla. The stamens protrude up above the narrow corolla which looks and smells very much like Jasmin. Relatively high temperatures during blossoming, especially if associated with a prolonged dry season, may cause flowers to be rejected by the tree. Unseasonably high winds can also reduce yields if flowers are blown off the plant prematurely. Well-defined wet and dry seasons lead to more pronounced flowering patterns. This occurs at the outer edges of the tropics in places like Minas Gerais in Brazil where long summer days (over 13 hr) tend to inhibit flower-bud initiation for 3 or 4 months.
- The Anther of a Stamen
- Anther of a stamen
- Peduncle (Stem)
After rainy season the flowers bloom and then they dry, fruit come out and flower fall down, then The coffee fruit is often referred to as a cherry or a berry, but in fact, it is a drupe. Other drupes include apricots, peaches and plums. Cherries are also classed as drupes, though berries are a separate category of fruit. (The confusion is compounded here when you consider that strawberries and raspberries are also not classed as berries.) The key to what defines a drupe is the built-in line of weakness in the outside of the pyrene (the stone or kernel) that splits apart and allows the seed to escape. This does not occur with berries such as grapes or red currants.
In this figure number B is a peaberry and A is normal coffee cherry, then a is skin, b is exocarp or pulp, c mesocarp, mucilage or pectin, d is endocarp or parchment , after that there is a skinny and papery layer which is silver skin and after that it is embryo which is the main part.
Peaberries, while sometimes considered a defect, are not associated with any flavour taints. In fact, many roasters tell us that because of the characteristic rugby ball-like shape of peaberries, they are easier to roast than ordinary beans. It is simply the loss of yield that is the problem. research into the formation of peaberries indicates that they are the result of environmental stress, but some plants are more prone to the production of peaberries than others. In some cases, the peaberry may account for as much as 40 percent of the crop. Plants prone to peaberry formation are usually removed from a farm because for every 1 percent of peaberries in a crop, there is a 0.75 percent loss of yield.a research study looking into drip irrigation of coffee plants found that in the first year of cultivation, the test plot without irrigation had a very high percentage of peaberries, at 21 percent of the total crop. The report states, ‘The production of peaberries is partially related to adverse environmental factors, mainly in the flowering and fruiting. So appropriate management of irrigation in these phases provided better conditions for the formation of beans, thus reducing the percentage of peaberries.’ Research demonstrated that air temperatures close to 24º C (1 degree above the upper limit of what is considered optimum for arabica coffee) increases the amount of peaberries harvested .