Ch 5 The Growing Environment - Heat Flashcards
Why does the vine need heat?
For successful flowering, fruit set and ripening;
What is the minimum temperature at which the vine will grow?
10 deg Celsius
Do all varieties need the same amount of heat?
No. Eg Riesling (cool) v Grenache (warm)
What are the main factors affecting heat/temperature?
Latitude, altitude, aspect, ocean currents, fog, soil, diurnal range, continentality
What are the main latitudes within which wine regions are found?
Between 30and 50 degrees north and south of the equator. This allows for a dormant period when the vine can rest.
What happens temperature at altitude?
As altitude increases temperature will drop so becoming cooler.
Exception to latitude rule is Cafayate in Argentina (26degSouth of equator but high altitude allows Torrontes grape to be grown)
Name three major current influencing wine regions.
Benguela Current : cools the Western Cape of S. Africa vineyards
Humboldt Current : cools Western Chile
Jet Stream : brings warmer wet air to European vineyards
How can fog help grape growing? Example?
Fog can cool a hot area allowing some types of grapes to be grown that would not otherwise be. It can also protect acidity and aromas.
Eg Pinot Noir in Los Carneros.
What is the heat benefit of stony soils?
It can retain heat during the warnth of the day and release this into the vineyard in the evening to prolong ripening
Which is better (for heat)? Dark or white soils?
Dark soils absorb heat better and can be critical in cooler climates.
What is meant by Aspect?
It is the direction that the slope of the vineyard faces towards the sun. The more southerly-facing (northerly- in southern hemisphere) the more sun received and generally tend to be hotter. This can affect the ripeness of the grapes.
Define Continentality.
It is the difference in temperature between the hottest and coldest months in the year ie height of summer, depths of winter
What temperature range does a region with high continentality experience?
High continentality means the region will experience a LARGE DIFFERENCE in seasonal temperatures.
What temperature range does a region with low continentality experience?
Low continentality means the region will experience a SMALLER DIFFERENCE in seasonal temperatures.
What does continentality determine for the grape grower?
a) the length of the growing season and total amount of heat available;
b) which grape varieties can be successfully grown.
Why might a region near a large body of water have a different continentality than an inland region?
Large bodies of water heat up and cool down more slowly than landmasses. They have a warming effect in winter and cooling in summer. Regions near water have low continentality whereas inland regions usually see extremes of temperatures and high continentality.
What is DIURNAL RANGE.
The difference between daytime and nighttime temperatures.
What impact does cool/ warm nights have on grape ripening?
Cool - help slow the loss of acidity and aromas in the grapes.
Warm - accelerate ripening
What factors can impact the diurnal range?
a) Proximity to lakes, seas and rivers
b) Cloud cover
What impact might proximity to water mass have on heat?
a) Proximity to lakes, seas and rivers - reflected heat overnight/ cooling breeze
What impact might cloud cover have on diurnal range?
Temps rise more slowly on cloudy days when sun cannot heat the ground directly - reduces diurnal range;
Temps fall more quickly on clear nights when no insulating blanket - increases diurnal range
Which part of the vine is most at risk from winter freeze? What can mitigate this?
The graft area. Earthing up can be used.
What impact might mild/ no winter have on the vine?
a) no dormant period so may overproduce - shortens life, quality diminished;
b) pests can survive and attack vines the following summer.
What impact might spring frosts have on the vine?
Can kill new budburst and young shoots. Enormous impact on yields
