The olive harvest: when and how it happens

The olive harvest in the northern hemisphere falls at the end of the year — broadly from around October to December, depending on the region, the variety and that year's weather.

The exact date is not a detail. It decides whether the oil will be a peppery, high-polyphenol early harvest, or a milder one with a higher yield.

How the fruit is picked

• By hand — the gentlest, least damaging to the fruit, and the slowest
• With hand combs or battery shakers that drop the fruit onto nets laid under the tree
• With trunk shakers that grip the tree and vibrate it
• With straddle harvesters that move along rows, in groves planted for the method

The nets under the tree matter in most methods. Olives that hit the ground bruise, pick up soil, and begin to deteriorate — and fruit gathered off the ground makes oil with higher acidity.

The hours that decide it

The moment an olive is picked, enzymes inside it begin breaking down the fats. That process does not pause while the fruit waits in sacks or crates under the sun.

Every hour before pressing adds free acidity, and acidity that has risen cannot be brought down again without refining — which would take the oil out of the extra virgin grade entirely.

This is why the distance between grove and mill has a real effect on quality, and why serious producers press within hours rather than days.

What happens at the mill

1. 1.The fruit is cleaned — leaves and twigs removed, the olives washed
2. 2.The fruit is crushed to a paste, once with stone mills, now usually with metal grinders
3. 3.The paste is stirred slowly in a step called malaxation, so small oil droplets merge into larger ones
4. 4.The oil is separated from water and solids, normally by centrifuge
5. 5.The oil is stored in stainless steel tanks, protected from light and air

Temperature matters at the malaxation stage. Warming the paste releases more oil, but it also breaks down flavour compounds and reduces polyphenols. Under European Union rules, "cold pressed" refers to extraction below 27°C.

Why a harvest date belongs on the label

Olive oil does not improve with age; it declines from the day it is pressed. A harvest date tells you how far along that process is — something an expiry date, counted from bottling, cannot do.