In order to determine the time to harvest the nut, one must think about what the fruits use will be.
Indeed, the coconut has a wide variety of uses, which means that harvests can happen at moments of varying maturity.
So, to get coconut water, the coconuts must be harvested still green and on the tree. The young coconut is more tender, and full of water. At this stage the nuts are envelopped in an important fibrous cover, that serves in the making of rugs or broom hairs, for example. So the picker must choose, by observing the color, the shape, and the weight, what is the perfect nut.
On the other hand, to make coconut chips or coconut oil, the nuts are picked later, when they are brown. The harvest of coconuts that have already fallen on the ground are for the making of coprah oil (an oil principaly used in cosmetics because of the process of refinement that removes a large portion of its nutrients).