Harvesting olives to get quality oil
Olives are ready to pick when there is sufficient oil in them to yield a fruity, not too bitter, slightly grassy oil. But how can you tell by just looking at them?
If the fruit is mostly green with little white dots on the skin it is not ready. The oil yield will be low and it will be unpleasant to taste - bitter and possibly metallic.
If the fruit is mostly black it could mean that it is past it's best state because the oil is likely to be bland. Unless it is Leccino or Pendolino, which may still not be ready to pick, even though the whole tree contains only black fruit.
If the fruit is a mixture of blush (rose coloured), black and straw coloured, it is most lkley ready to be picked.
If the whole tree is covered with straw-coloured olives, they could be ready (as is the case with Frantoio sometimes).
If you are not sure, cut open an olive to see what colour the flesh is. If it is green it's not ready. If it's turning a purple colour it most likely is. Squeeze an olive to see how much oil oozes out. This will help you decide whether it's ready or not.