As more and more of our customers become increasingly interested in the source, provenance and authenticity of our wonderful Morocco Gold extra virgin olive oil, they are becoming increasingly interested in how our olives are grown.
We are delighted to share a series of articles that provide some information on the life cycle of this most wonderful of fruits.
Olive trees can produce olives for hundreds of years. Yet olive trees typically alternate between bearing small crops and normal crops every other year. They can also go for 2 – 3 years without bearing any fruit. There are a number of key stages in the life cycle of the olive tree that lead up to the harvesting and pressing of our extra virgin olive oil.
Olive trees produce fruiting shoots called inflorescences, which originate at the axil of a leaf. Each inflorescence will typically contain 10 to 30 flowers depending on the type of olive. The number of flowers that then mature into olives dependent on a number of factors.
The ‘Goldilocks’ Zone
Olive trees require temperatures that are – not too hot – not to cold – but just right!. They require winter cold to achieve normal blooming and fruiting. The optimal degree of cold winters is dependent upon the origin of the olive cultivar (e.g. Eastern Mediterranean vs. Southern Europe). Strong winds, hot temperatures, and freezing temperatures can negatively impact fruit set. Particularly cold springs will negatively impact harvest by delaying blooming and increasing flower abnormalities. Localized winter temperature rises due to development around the tree such as buildings and asphalt can act as a wintertime heat sink, thereby inhibiting fruiting.
The remote, elevated valley in the foothills of the Atlas Mountains provides the ideal balance of temperature throughout the olive growing season.
Before flowers bloom, they go through a differentiation period that has to do with the sexuality of the blooms. This generally takes place March through May and results in one of two results (although there is some new research indicating that there may be a third possible result).
Flowers which have both stamen (the male part) and pistil (the female part)
Flowers which have only stamens and lack a pistil (which apparently have been aborted)
Why are there staminate flowers and not just perfect (hermaphroditic) flowers? There are a number of theories and reasons, but the main ones are thought to be :
- It takes a great deal of energy to develop the pistil (or ovule – think of this like the human ovum). The tree has to moderate the number of pistils it is able to develop with the nutrients available to it.
- In order to pollinate the pistil, the tree is dependent on a high volume of stamens – stamens don’t have the same nutrient requirements as the pistils, so the tree exercises her “nutrient economizing” by terminating pistils (ovules) as needed.
Orchard stress, in particular water stress, can negatively impact this portion of development. In competitions between flowers and leaves, the leaves win, and the first floral part to fail is the pistil. A moist soil profile during this period can help prevent this kind of stress.
Pistil abortion occurs naturally and is not perfectly understood. Pistil formation must compete with vegetative growth for nutrients at a time when both are working their hardest. In addition, following a big harvest year, the tree’s nutritional resources have been depleted. Yet, if only 1% – 2% of the flowers are able to set fruit, the grower will still enjoy a satisfactory crop. If a tree is blooming, but no olives develop, this could be because of a mechanical disruption to fruit set. Wind, rain, and/or hail can knock off the blooms just at this critical time of the year.
According to the Olive Production Manual (University of California, Agriculture and Natural Resources), “…some 500,000 flowers are present in a mature tree…” at time of full bloom. Within two weeks of full bloom, most of the flowers will have failed, with only 1 – 2% then maturing into full-grown fruit.
Because of their geometry, olive flowers self-pollinate. The anthers (located at the top of the filaments attached to the stamen) drop pollen on the stigma of the pistil. The pollen grains germinate and olive growth is underway. Though not necessary for pollination, wind and bees may aid in pollination by disturbing the flower causing pollen to fall from the anther to the stigma. Many olive varieties cannot self-pollinate. For these trees, olive pollen is primarily carried by wind. Bees may play a minor role in pollination.
Cross-pollination occurs when wind or a bee transfers pollen from one flower to the stigma of another flower. As bees are not particularly fond of olive flowers, they do not typically play a large role in the olive orchard.
Stress – It’s Not Good For Olives Either!
As with us humans, stress on the olive tree and it’s fruit will be detrimental. This may be caused by a number of factors including too much or too little pruning, shortage of water – when the tree will favour the leaf over the fruit and pest infections.
The Annual Cycle
Ground work and tillage is carried out once or twice a year: once in winter to facilitate rainwater infiltration into the soil, and in spring to rotate the soil. Any planting is done at the beginning of spring.
In addition to natural rainfall, which is generally sufficient in the geographical area, trees are irrigated as needed during the period of vegetation of the olive tree, normally until the end of September.
Fruiting sizing and assessment of the maturity of the olive is carried out annually. The planned date of harvest is agreed based on the maturity index of the olives, also the generations of experience of the olive farmers. Harvesting will then normally take place between the end of October and beginning of December.
Morocco Gold olives are harvested by hand using flexible combs. Nets and tarpaulins are placed on the ground to avoid contact between the olives and the ground.
Breton, Catherine, André Berville. “From the Olive Flower to the Drupe: Flower Types, Pollination, Self and Inter-Compatibility and Fruit Set.” Intechopen.com. Intech. 10 April 2013. Chapter 12. Web. 25 May 2017.
G. Steven Sibbett and Louise Ferguson: Olive Production Manual, University of California, Agriculture and Natural Resources, Publication 3353, 2005. Print.
“Third Gender Identified in a Close Relative of the Olive Tree.” PHYS.ORG. Science X Network, 30 March 2010. Web. 25 May 2017