When to harvest olives: deciding with the maturity index

There is no calendar answer to "when are olives harvested?" The right moment shifts by weeks according to place and variety, and changes completely depending on whether you are picking for oil or for the table. The measure used is not the calendar but the colour of the fruit.

The short answer

In Türkiye the olive harvest generally runs from early October to early January. Within that window:

• Green table olives come first: late September to early October, while the fruit is still fully green.
• Early oil harvest falls in October, as the fruit turns from green to pink.
• Ripe oil harvest falls in November, once the fruit has turned purple-black.
• Black table olives come last: late November to December, at full black.

Region matters too. The same variety ripens weeks earlier on the Mediterranean coast than around the Sea of Marmara.

The measure: the maturity index

Harvest timing is set using the maturity index developed in Jaén, Spain and adopted internationally. It classifies skin and flesh colour from 0 to 7:

Broadly: 1–2 is green ripening, 3–4 pink, 5–7 black.

How the index is calculated

A representative sample is taken — 100 fruits collected from all four sides of the tree and from different heights. They are sorted into the eight classes, each class count is multiplied by its class number, and the total divided by 100.

Example: of 100 fruits, 10 fall in class 1, 40 in class 2, 35 in class 3 and 15 in class 4.

(10×1 + 40×2 + 35×3 + 15×4) ÷ 100 = (10 + 80 + 105 + 60) ÷ 100 = 2.55

The target range for an oil harvest is usually 3–4. The grove in this example is slightly early; another week would help.

The average is not the whole story. Distribution matters as well: most fruit should sit between 2 and 5, without large numbers at the 0–1 or 6–7 extremes. A grove averaging 3.5 because half is green and half overripe is not the same as a uniform one.

Early or late?

This is a quality-versus-quantity trade, and both sides of it are real.

Harvest early and you take less oil from the tree, but the oil you take is more phenolic, more aromatic and more stable. Harvest late and oil per kilo rises while bitterness, pungency and keeping quality fall.

Bitterness and a peppery catch in the throat are not faults but signs of phenolic content — see oleocanthal and polyphenols.

To see how yield shifts with harvest timing in your own grove, use the yield calculator.

The cost of waiting

Delaying the harvest does more than lower oil quality; it brings two concrete risks.

Olive fruit fly. Ripening fruit becomes more suitable for the fly, and every week the crop hangs raises the risk of infestation. See olive fruit fly control.

Free acidity. Fruit that has fallen, been bruised or kept waiting develops higher acidity — the threshold that defines the extra virgin grade. See what acidity means in olive oil.

A late harvest also reduces next year's crop. While fruit hangs it continues drawing on the tree's resources, weakening flower bud formation for the following season and deepening alternate bearing.

Ripening by variety

Ripening time is a fixed characteristic of the variety. Some of those recorded on this site:

For a grower with several varieties, this table means the harvest is run in sequence, not in one pass. Picking Erkence and Memecik on the same day means picking one too early and the other too late.

Why table harvest is different

For table olives the measure is not oil but texture and size.

Green table olives are picked once the fruit has reached full size but before colour change begins (MI 0–1). Left later, the flesh softens and breaks up in brine.

Black table olives are the reverse: picked after colour change is complete (MI 5–7). Picked early, they fail to wrinkle, do not take salt properly and taste flat.

Table harvest must also be done by hand. Fruit that has fallen or been struck cannot be used; bruises darken in brine. Harvesting methods acceptable for oil fruit are not usable for the table.

Frequently asked

Which month is the olive harvest? October to December in Türkiye, extending to late September for green table olives and into late December for black.

Can fallen olives be collected? For oil, yes, but they must be processed separately. Acidity rises quickly in fruit left on the ground, and blending it into good fruit can downgrade the whole batch.

How quickly must the harvest be processed? Harvested fruit left waiting heats and ferments. The rule is to mill on the day of picking; fruit left in sacks is the main source of the fusty defect.

Does harvest timing affect alternate bearing? Not directly, but it helps. An early harvest leaves the tree more time to form next year's flower buds and softens the on-off cycle.

Sources

• Maturity index (Jaén scale), classes 0–7: assessed on skin and flesh colour following the International Olive Council method. For the class definitions see Sola-Guirado et al., "A Machine Vision Rapid Method to Determine the Ripeness Degree of Olive Lots", Sensors 21(9): 2940.
• International Olive Council, sensory assessment standard for virgin olive oil COI/T.20/Doc. No 15 — definition and origin of the fusty defect.
• Ripening times by variety: zeytin.net variety database. Detail for each is on its variety page.