Berry ripening and temperature

Above 50 F, the vine and each berry are metabolically active. Therefore, temperature has a direct effect on when phenological events, vegetative growth and ripening occur. The calculations below are for quantifying the growing season length and range. However in terms of relevance, it goes on the list of “Things to do between Oct and Mar”.

Growing Season:
Comparing heat summation between sites or vintages*

  • heat summation or heat available to develop canopy + fruit (in hours)
    =SUM (hourly_temps_Apr1_Oct31 – 50 F)
  • heat summation/month or length of growing season in hours
    eg. WA, affects planting decision on varieties with short bud break-to-ripeness window.
    =SUM (hourly_temps_Apr1_Apr30 – 50F)
    =SUM(hourly_temps_Oct1_Oct30 – 50F)

Ripening temperatures

  • day, night and diurnal differential during ripening (in F)
    comparison with regions, vintages per variety per site.
    =AVG (hourly_temps_day_verais_to_harv)
    =AVG (hourly_temps_night_verais_to_harv/hr)
    =AVG (hourly_temps_night_verais_to_harv – hourly_temp_day_verais_to_harv)
  • day and night heat summation during ripening per variety per site (in hours)
    =SUM (hourly_temps_day_verais_to_harv – 50F)
    =SUM (hourly_temps_night_verais_to_harv – 50F)

Other climatic data relevant to berry ripening or in some cases berry damage:
sunlight (approx 10% of full sunlight required to develop color or anthocyanins in skins) wind (slows down photosynthesis rate (stomata close so less CO2 uptake) and therefore sugar accumulation) precipitation (winter kill, frost, hail, heat damage, bunch rots)

Further reading:
Greenspan, Mark. Climate and the Ripening Process. Wine Business Monthly. Aug 2007
Greenspan, Mark. Climate Change. Wine Business Monthly. June, 2007. pp. 52-57


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