The development of an olive is marked by three perfectly sequenced phenological phases; in each of them, the fruit builds a different resource: first volume, then structure, and finally oil. We are now in Phase 2, the lignification of the pit. This is a key moment in agronomic management when the goal is to produce extra virgin olive oil of the highest quality. Based on our agronomic experience and supported by current scientific research, this article explores what is currently happening in olive groves and explains the biological sequence that defines every great extra virgin oil.
Phase 1: Rapid Cell Growth (Division and Expansion)
When? Late May to late June, in Mediterranean olive groves. After pollination and the formation of the first fruits, the olive begins its first growth spurt. During the following five to six weeks, the fruit's mission is simple: multiply cells and expand them. Up to 80% of the cells that will house oil are formed during this brief window. New cells appear while existing ones fill with water and sugars, allowing the olive to double its diameter in just one month. The pit remains soft, forming but not yet lignified. What won't you find yet? Oil. Lipid bodies only appear when the pit hardens, so the oil content in Phase 1 is practically zero. Why is this phase crucial? Think of each new cell as a "vat" that will later be filled with oil. If its production is limited now by heat, water stress, or lack of nutrients, the fruit will not be able to compensate later, even if conditions improve. Indicators in the field:
- 10 days after fruit set: olives look like small green pearls, still translucent.
- ≈30 days after fruit set: diameter reaches ~1 cm; the growth curve levels off. If the pit resists gentle pressure, Phase 1 ends and Phase 2 begins.
In short, Phase 1 focuses on building capacity. The tree defines the cellular architecture that will contain the oil, aromas, and antioxidants that give extra virgin oil its value. [caption id="attachment-17348" align="aligncenter" width="850"]
Source: Research Gate[/caption]
Phase 2: Pit Lignification (Endocarp)
When? Early July to early August, depending on variety and climate. After the first growth spurt, the olive pauses to build its "armor." During Phase 2, the endocarp deposits lignin and becomes the rigid pit that will protect the seed, according to this study. What happens inside?
- Lignin formation: Cells stop dividing and concentrate lignin in their walls, converting flexible tissue into hard stone.
- Slowdown in growth: Resources are diverted to lignification, temporarily stopping mesocarp expansion.
- Physiological turning point: Once lignification is complete, biochemical signals awaken oil synthesis; lipogenic enzymes come into action, marking the beginning of Phase 3, as explained by this work.
Why is it important? The completion of lignification marks the actual beginning of oil accumulation. In Mediterranean varieties, it is usually completed 80 to 90 days after flowering: mid-July for Arbequina and late July-August for Lecciana or Koroneiki. With the seed protected, the fruit better withstands short water deficits: many producers reduce irrigation to control vigor without affecting yield, according to this study. Field insights:
- The weekly diameter curve stabilizes.
- When gently squeezed, the pit is firm and does not yield.
- The skin remains green; color change is not observed until mid-Phase 3.
Phase 2 is all about structure: the olive builds its shell and activates its metabolism to store oil.
Phase 3: Maturation and Oil Accumulation (Lipogenesis)
When? Early August to late October, depending on variety and altitude. In Phase 3, the olive resumes its growth in diameter, but the real change is in the weight and oil content. Mesocarp cells fill with triglycerides thanks to enzymes that convert stored sugars into lipids. Oil accumulation intensifies after lignification, for six to eight weeks, increasing the oil/weight ratio until mid-October. Simultaneously, the fruit generates phenolic and aromatic compounds: oleuropein derivatives, flavonoids, and volatile precursors. These compounds define the bitterness, pungency, color, and antioxidant capacity of high-quality oil. They rise with the oil, peak early, and decline as maturation progresses, according to this article. Each week of maturation influences the oil's style and commercial positioning: Early harvest: green fruit provides intense, herbaceous, bitter, and slightly pungent oils, rich in polyphenols. Highly valued in haute cuisine, though with lower yield. Late harvest: as it acquires purple tones, the olive increases triglycerides. The oil is softer, rounder, and fruitier, with better yield and lower phenol content, ideal for a wider audience. In summary, Phase 3 offers:
- Early harvest: intensity, gastronomic prestige, high polyphenol content.
- Late harvest: higher volume, soft flavor, and commercial versatility.
Conclusion
Phase 1 builds the fruit's "cellular storage units," Phase 2 hardens the pit and activates metabolic change, and Phase 3 fills each cell with oil and phenolic compounds that determine flavor, color, and shelf life. Interpreting these phases allows harvesting at the optimal moment, when chemistry, aroma, and yield are aligned, ensuring extra virgin quality year after year.
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Sources:
- Camarero, M. C., et al. (2023). Characterization of transcriptome dynamics during early fruit development in olive (Olea europaea L.). International Journal of Molecular Sciences, 24(2), 961. https://doi.org/10.3390/ijms24020961
- Elsayed, S. M., et al. (2013). Growth curve of fruit development stages of three olive cultivars. Middle East Journal of Agriculture Research, 2, 25–30. https://www.curresweb.com/mejas/mejas/2013/25-30.pdf
- Rosati, A., et al. (2023). From flower to fruit: Fruit growth and development in olive (Olea europaea L.)—a review. Frontiers in Plant Science, 14, 1276178. https://doi.org/10.3389/fpls.2023.1276178
- Gucci, R., et al. (2009). Water deficit‑induced changes in mesocarp cellular processes and the relationship between mesocarp and endocarp during olive fruit development. Tree Physiology, 29(12), 1575–1585. https://doi.org/10.1093/treephys/tpp086
- Sánchez‑Piñero, M., et al. (2022). Endocarp development study in full irrigated olive orchards and impact on fruit features at harvest. Plants, 11(24), 3541. https://doi.org/10.3390/plants11243541
- Rapoport, H. F., & Pérez‑López, D. (2013). Fruit pit hardening: Physical measurement during olive fruit growth. Annals of Applied Biology, 163(1), 45–51. https://doi.org/10.1111/aab.12046
- Sánchez‑Piñero, M., et al. (2024). Assessment of water stress impact on olive trees using an accurate determination of the endocarp development. Irrigation Science. https://doi.org/10.1007/s00271-024-00914-w
- Skodra, C., et al. (2021). Olive fruit development and ripening: Break on through to the “-omics” side. International Journal of Molecular Sciences, 22(11), 5806. https://doi.org/10.3390/ijms22115806