Welcome the final part of our Coffee Tree Management Series. If you haven’t read Part’s 1 and 2 then you can find them here:
Part 1 – Tips, Techniques and Challenges
Part 2 – Growth and Maintenance
Flowering and Harvesting
Flowering takes place on lateral and secondary branches. It requires a dry stress period and then a rainy period to induce a consistent and uniform flowering. Coffee is largely self-pollinating, which means flowers from the same tree can pollinate one-another. Occasionally sterile starflowers form caused by too high temperatures or a lack of temperature difference between the seasons in a year. Often only about 20% of flowers will become ripe fruit due to pests and weather. A flower goes through a number of stages before it becomes what you might recognise as a coffee cherry: node formation, pinhead stage, bean expansion, ripening. The development time taken from flower to ripe fruit will, depend on location, altitude and climatic factors but it’s usually around eight months. Around 5% of cherries will form and ripen outside of the usual harvest periods. In some countries coffee has two harvests; a main crop and a fly crop, usually smaller.
In your second year it’s likely you will receive your first small harvest but the first year of full production will be achieved in your third year. The majority of Arabica varieties produce red cherries (although yellow varieties are also common) and these should only be harvested when the whole cherry is a uniform red colour, indicating full ripeness. Because cherries within the same cluster may not ripen at the same time it requires repeated harvests from the same tree. Choosing only the ripe cherries makes processing easier and prevents causing damage to the tree for future harvests. Practices like strip picking and machine harvesting, although quicker, retrieve a lower quality of cherry and will often result in a lower cup quality.
After a number of years the vigour of the tree to produce new fruit bearing branches decreases, meaning it needs to be cut down in order to regenerate, this is known as stumping. This is a common practice for many perennial agricultural crops. The act of stumping will cause the root structure to die back, which in turn causes the plant to produce new growth in the form of roots and branches. From this new growth a ‘new’ coffee tree will form. Once trees have been stumped they will take time to grow back and produce their first harvest. This can take one or two years from cutting. Stumped trees become similar to seedlings again so during this re-growth phase care must be taken to water the plants and control weeds again. Nevertheless, it is also a good opportunity for inter cropping.
In a high input system trees may be stumped every 3-4 years whereas in an area with limited resources trees may be left for 7-8 years without being regenerated. Stumping can also be done if the farm is heavily infested with disease or pests. Different types of stumping exist:
- Full Stumping – where all trees in a plot are completely cut down.
- Mother Stumping – where all branches are cut down apart from one, so the trees can still photosynthesise. Note, this requires a trees to already be stumped once to produce a multi stem tree.
- Selective Stumping – certain trees in a plot are stumped if considered to be under-producing, but the tree next to it may be kept as it is.
Selective stumping allows for better management of individual trees, but after a number of years can be confusing for the farmer to try and remember how old each tree is and therefore how much fertiliser to apply and when it might need stumping again.
Trees should be cut with a saw about a foot from the ground at a 45 degree angle to allow rain water to fun off. If water is allowed to collect in the open cut it can be susceptible to bacterial and fungal infections. Once the tree has been cut, the sides of the stump can be scratched to break the bark. This helps to promote new growth from those areas, meaning you have more control of where the new stems will form. After a few weeks a number of new suckers will have spouted which then gives you the opportunity to decide how many stems you would like to develop. The number will depend on the variety, your management system and your plant spacing but the recommended number is between one and four. Choose the strongest suckers and preferably equally spaced apart around the stump.
To avoid stumping all your trees at once and therefore loosing out on production and income for a year, it is possible to divide your farm into sections and fully stump them in successive years as shown in the pictures below. Stumping cycles are perhaps one aspect of coffee tree management that varies most amongst different coffee producing regions. In Central and Latin America, trees are typically pruned to have one main stem. In Africa, it is typical to prune trees for multiple stems per. So, although tree-planting densities typically are much lower in Africa, each tree is producing relatively more because there are multiple main stems. How many plots the land is divided into can depend on whether the farmer is working on a high or low input system.
To the average coffee drinker little thought may be given to the difficulties and need for technical knowhow that arise when growing coffee. The reality is that a coffee farm requires lots of attention to a number of complex stages that all interact with one another. In each coffee growing region, farmers have developed their own techniques to suit their system. A farm is a business, and like any business there are a myriad of factors that will change the inputs required, and the resulting outputs obtained. However, the most important input, and the one that can’t be controlled by the farmer, is that of the climate. Although this is not a specific topic of coffee tree management I thought it was very important to mention as it is the number one factor affecting the longevity of coffee production. Many of the world’s smallholder coffee farmers are based in somewhat unstable areas of the world, be that politically, geographically or climatically. Any negative implications of these factors are multiplied when resources are limited, reducing the ability to adapt and overcome challenges. Changes in climate can disrupt every stage of coffee tree management. Changing rainfall patterns and increased temperatures will cause long term drought stress periods, affecting planting, the growth of trees and flowering. An abundance of rainfall will exacerbate erosion and nutrient leaching problems, not to mention landslides and floods. Changing seasonal patterns make pest infestations harder to predict and manage. The plan for each stage of coffee tree management needs to be to be mapped out in a way to try and mitigate the difficulties caused by an uncontrollable, and ever increasingly, unpredictable climate.