Below are a Rainfall, Average Maximum (AV Max) and Average Minimum Temperatures (AV Min) table of Hartswater, as well as of all the major Olive Growing Regions in the World. You can compare your own data to this and should you fall within these, you stand a very good chance that Olives would grow and produce good yields.

The Effects of Chilling on alternate bearing

Chill units

  1. Olea Europaea is an obligate thermoperiodic species that requires at least 10 weeks below 12.2° C to13.3°C for full expression of flowering (Schaffer et al, 1994)
  2. Different cultivars require different no of days of chilling to set fruit (Denney et al, 1983; Hartmann et al 1975) ranging from 600 hrs to over 1000 hrs Cirik, 1989).
  3. Temperatures over 16° C decrease flower bud formation whilst temperatures below 12° – 13°C stimulate it (Alaca et al, 1992; Hackett et al, 1967; Hartmann et al 1975).
  4. The olive needs a sufficient number of days below a threshold temperature (+/-7.2° C) to allow flower bud differentiation (Maracchi et al 1994).
  5. Trees held at a constant temperature of 7°C produce very little flowers or even fail to bloom.
  6. Highest flowering production was obtained with a diurnal sine wave temperature having 15°C maximum and a 2°C minimum for 70 to 80 days.
  7. Fewer inflorescences were produced on trees exposed to a similar fluctuating temperature pattern of 7° to 18° C to 12,5°C constant, or to a 2° to 15°C temperature pattern changing from one extreme to the other.

Note: The presence of leaves during chilling is a requirement for flower initiation. (Hacket et al 1964; Hartman et al 1975).

Flowering

The pollination of the olive is carried out mainly by wind and thus it is important that the atmospheric conditions such as rain, strong wind, excessive high or low temperatures, particularly when accompanied by dry wind, causes abortion of young fruitlets (Marracchi et al, 1994; Monselise et al, 1982)

The optimal condition for flowering is between 15° and 20°C (Narciso et al,1992). Best pollination occurs when the temperature is between 19°C and 22°C (Msallem et al, 1996). Temperatures < 10°C reduced pollination (Schaffer et al, 1994) whilst it has been shown that pollen tube growth in the ovary is inhibited when the temperature during flowering rises above 30°C (Griggs et al.1975, Fernandez-Escobar et al. 1983). Under such conditions, very low fruit set might occur or a considerable number of inflorescences with small parthenocarpic fruits (shot berry) may develop (Bradley, 1961). Cross pollination is particularly important under these conditions since foreign pollen allows normal pollen tube development in the style even at these relatively high temperatures

Climatic Regions of the world

Please note: If you have a temp of lower than -7°C, I would not recommend the planting of Olive Trees.

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