Increased moisture levels, (perhaps accompanied by an increase in daylight hours), stimulate the coffee tree to blossom. This blossoming is accompanied by pollination, and then the development of fruits. In Brazil, this usually occurs in September and October. The coffee reaches maturation and is ready to be picked 8-9 months after fertilization. The problem with multiple rainfalls throughout the springtime is that it leads to various blossomings, and therefore various levels of maturation on the same branch when it comes time to pick. (See photo above. From left to right: over-ripe, ripe, and green, or unripe.)
This means that either the same coffee tree most now be picked more than once (in the case above, three times), or it must all be picked at once and the green (unripe) coffee sorted out later. The cost of going back to pick three times is quite high. Brazil, fortunately, has some of the best labor standards compared to other producing countries. This means that the cost of sending someone back to hand pick only the ripe is quite high and oftentimes cost-inhibitive. Removing green coffee after picking requires a rather extensive infrastructure to which few have access. For naturally processed coffees, where the coffee seeds (beans) are dried in the cherry, the process of removing the green is even more difficult than in the pulped natural or washed processing methods since all of the coffee maturations are dried together. In pulped natural coffees, the coffee is pulped right away (before drying) and the machine can be adjusted to pulp only the ripe coffee. (Think about how much harder it is to peel an unripe banana vs a ripe banana). However, roughly 80% of the Arabica coffee produced in Brazil is naturally processed.
Why can’t they just pick the ripe and leave the rest on the vine to fall off, decompose, and act as an organic fertilizer?
Unfortunately, coffee left on the tree creates a myriad of problems, the main one of which is broca, an insect that bores its way into the coffee bean where it eats the bean and plants larvae. Leaving coffee on the tree provides an ideal environment for them and can devastate the next year’s harvest.