The olive tree, Olea europaea, is a subtropical evergreen tree from the Oleaceae family that is native to the Mediterranean, Africa and China. They grow best in areas with a Mediterranean climate, which is characterised by a long, hot, dry summer growing season and a relatively cool mild, wet winter.
Most of the world’s olives are grown in the Mediterranean region, where they have been cultivated for thousands of years. There is evidence of olives were being grown and used for oil production on the Greek island of Crete as early as 3500 BC, and olive oil is a common ingredient in Mediterranean cuisine, having its origins in ancient Greek and Roman cuisine.
Both olives and olive oil are known for their diverse culinary uses and health benefits, and as such are used for food, cooking, medicines, salves, and soap production. Olive oil was also used traditionally as a lamp fuel for lighting.
Olive Nutritional Value
Nutritionally, olives and olive oil are good sources of healthy monounsaturated fat, primarily oleic acid. Of all the edible oils, olive oil has the highest percentage of monounsaturated fat, with over 70% in content.
They also contain other compounds with antioxidants properties that offer protective health benefits, such as carotenoid and chlorophyll pigments, vitamin E (in the form of alpha-tocopherol), and phenolic compounds (such as hydroxytyrosol, tyrosol, oleocanthal, and oleuropein), as well as a sub-category of phenolic compounds known as flavonoids (which include the compounds apigenin, luteolin, quercetin, and rutin).
Olive Tree Pollination and Fruiting
Olive trees vary in size, depending on the variety, ranging in height from 3-12 metres (10-40′) or more. They bloom in late spring, producing loose clusters of small, whitish flowers, and there are two types of flowers produced.
- The first are botanically know as ‘perfect flowers’, as they contain both male and female parts, and are capable of developing into the olive fruits.
- The second type of flowers are male flowers, which contain only the pollen-producing parts for pollination, and do not develop into olives.
The flowers of olives are wind-pollinated, and they may set fruit inconsistently at times. In areas where olive trees do not receive proper irrigation and fertiliser, they tend to biennial cropping, where they produce a heavy crop one year and set very little fruit in the following year.
The pollinated flowers develop into olive fruit, which are classed botanically as a drupe, otherwise known as a stone fruit, similar to peaches, plums, cherries and other fruit which have a stone or pit in their centre. Within the stone of an olive are one or two seeds.
The olive fruit will reach their greatest weight 6-8 months after the blossoms appear and will have maximum oil content or 20–30% of fresh weight (measured with the pit removed). At this stage they will become black in colour and remain attached to the tree for several weeks.
Olives can be picked at various stages though, from when they’re green in colour all the way until they’re black, depending on how we wish to preserve them for eating. Understanding when and how to pick olives is crucial to ensure the best quality and flavour.
In this article, we’ll explore the factors influencing the timing of olive picking and the ways to harvest them efficiently.
When to Pick Olives
As olives ripen, they change from green to yellow-green, straw, rose, red-brown, and finally dark red to purplish black. They can be harvested at all of these stages, but their ideal picking time depends on the variety of olive and how we intend to use them.
Olives need to be prepared for eating because they contain bitter compounds and other substances that make them unpalatable and inedible to be eaten fresh. Various preparation processes, such as curing or brining are used to make olives safe and enjoyable to eat.
To prepare green olives, they must be harvested before they fully ripen, while black olives are picked when fully mature. Here are some general guidelines on picking green and black olives:
Harvesting Green Olives
Green olives are ready to be gathered when they have reached their full size, but before they turn fully black. The color should be mostly green with a slight blush. The flesh should be firm, and mature green-ripe olives will release a creamy white juice when squeezed.
When harvesting olives for use with green olive preparation methods, they are mainly harvested commercially when they are an even colour from yellow green to a straw colour. The olives can still be used as they ripen further, changing from yellow-green to rose to red-brown, as the flesh is still firm at these stages of ripening and lacks dark pigment, or is partially pigmented close to the skin.
Harvesting Black Olives
Black olives are picked when they have been allowed to ripen fully on the tree and have turned fully dark red to purple or black about 3-4 months after the green-ripe stage, depending on the variety.
They should be plump, shiny, and slightly soft to the touch. Ripe olives bruise easily and must be handled with care. Mature dark olives will release a reddish-black liquid when squeezed, and their flesh will be nearly completely pigmented.
The oil content of olives increases as they ripen, and black ripe olives are therefore primarily used for oil extraction, as well as for preparing black olives for eating.
If the flesh of black olives is pigmented all the way through to the stone, they’re considered overripe, meaning that they will be a lot softer when processed, but that me be preferred when making dried olives.
What Time of The Year Are Olives Harvested?
Olives are typically harvested in late summer through to the early autumn months, generally around the months of March to May in the southern hemisphere and September to November in the northern hemisphere.
The exact timing of the olive harvest can vary depending on climate, and olive variety.
Olives ripen more quickly in warmer climates, so the harvest times may vary depending on the location.
Additionally, olive trees can be categorised as early, mid and late season varieties due to their ripening times. Some may mature earlier in the season, while others may take longer.
- Early season varieties – mature earlier in the season and may be ready for harvesting as early as late summer.
- Mid-season varieties – mature around mid-autumn, this is the time when many olive varieties are typically harvested.
- Late season varieties: – mature around late autumn.
The timing of the harvest is important because it impacts the flavor and quality of the olives, and how they can be used. Green olives are usually harvested before they fully ripen, while black olives are picked when fully mature, so it’s crucial to monitor the ripeness of the fruit to determine the best time for harvesting
How to Pick Olives from Trees
Once we know when to pick olives, we need to understand the proper techniques for harvesting olives from the trees to avoid damaging them, as we should only select freshly harvested, unbruised olives for processing.
To gather olives, we need the following tools:
- Gloves to protect our hands from the bitter compounds present in unripe olives.
- Collection containers such as baskets or buckets to collect the harvested olives in.
- Secateurs (pruning shears) to gently remove olives from the tree without causing damage, or, as another option.
- Plastic olive hand rake to gently dislodge olives from the tree without causing damage, and an olive harvesting net (piece of shadecloth or a plastic tarp sheet to catch falling olives).
Two techniques for harvesting olives are hand-harvesting and using special hand rakes.
1. Hand Harvesting Olives
When trees are small in size and not too tall, hand harvesting is a convenient method for gathering olives.
- For green olives, use secateurs to cut the olive clusters from the branches to avoid bruising or damaging the fruit.
- For black olives, pick by hand, gently grasping and twisting the fruit to release it from the stem. Be careful not to damage the tree or the bruise the other olives.
2. Harvesting Olives Using Hand Rakes
Hand rakes, also known as olive combs, are small plastic rakes designed for olive harvesting, and are helpful for collecting olives from larger olive trees. Some have hollow handles that can be attached to an extension pole to reach into tall olive trees.
To use an olive rake, starting near the trunk of the tree, run the rake gently along the branches towards the branch tips dislodge the olives without harming the tree. The rake will pluck the olives from the branches, causing them to fall to the ground.
To catch the olives falling to the ground when using a plastic rake, an olive harvesting net is placed below the tree. Many commercial olive harvesting nets are simply made of shadecloth, so it’s possible to use a large sheet of shadecloth or a clean plastic tarp sheet for the purpose.
Incidentally, it’s not viable to just wait for olives to drop on their own onto a harvesting net fixed below a tree, as the process will take way too long, and the olives will end up becoming overripe for most uses.
Useful Tips:
- When gathering olives, don’t put too much into a single collection container, as this can squash the fruit at the bottom, which can lead to bruising and spoilage.
- Olives can be pruned after harvesting, they fruit on one-year-old wood, so cutting new growth back by half will reduce the canopy size and promote new branching to increase fruiting while leaving enough fruiting wood for next the year.
Sorting and Storing Harvested Olives
After harvesting, sort the olives based on ripeness and quality. It’s best to process fresh olives within a few days after harvesting them to maintain freshness. Green olives generally store better than black ripe olives.
To maintain the best quality, store them in well-ventilated containers such as shallow, ventilated crates at temperatures between 5-10°C (41-50°F). Prolonged storage of 6 weeks or more at 10°C (50°F) can cause pitting and spotting on the surface of the olive.
Avoid airtight containers to prevent mould growth. Also, avoid storing fresh olives at colder temperatures from 0-2°C (32-36°F) for 2 weeks or more, as this can cause chill injury that will lead browning of the skin and flesh of the olives.
Foraging for Olives in Public Spaces
Olive trees are sometimes seen growing in public spaces, and unharvested trees end up dropping all their fruit to the ground below to create a bit of a mess, which is a huge waste of an excellent resource. Established trees can produce very large crops of olives, which can be harvested, and processed to preserve them for use throughout the year. By knowing when olive tree crops are produced, we can observe the crops ripening week by week to select the optimal harvest time.
I’ll add an article soon on how to process olives! Happy olive picking!
References
- University of California, Division of Agriculture and Natural Resources, PUBLICATION 8267, Olives: Safe Methods for Home Pickling. <https://anrcatalog.ucanr.edu/pdf/8267.pdf>
- Olive harvesting and preserving. (2023, March 15). Organic Gardener Magazine Australia. <https://www.organicgardener.com.au/blogs/olive-harvesting-and-preserving>
- The Editors of Encyclopaedia Britannica. (2023, September 8). Olive | Description, Production, & Oil. Encyclopedia Britannica. <https://www.britannica.com/plant/olive-plant>
- Olea europaea (Common olive, European Olive, Lady’s Oil, Sweet Oil Plant) | North Carolina Extension Gardener Plant Toolbox. (n.d.). <https://plants.ces.ncsu.edu/plants/olea-europaea/>
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