Ch 5 The Growing Environment - Heat

Question 1

Why does the vine need heat?

Answer 1

For successful flowering, fruit set and ripening;

Question 2

What is the minimum temperature at which the vine will grow?

Answer 2

10 deg Celsius

Question 3

Do all varieties need the same amount of heat?

Answer 3

No. Eg Riesling (cool) v Grenache (warm)

Question 4

What are the main factors affecting heat/temperature?

Answer 4

Latitude, altitude, aspect, ocean currents, fog, soil, diurnal range, continentality

Question 5

What are the main latitudes within which wine regions are found?

Answer 5

Between 30and 50 degrees north and south of the equator. This allows for a dormant period when the vine can rest.

Question 6

What happens temperature at altitude?

Answer 6

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)

Question 7

Name three major current influencing wine regions.

Answer 7

Benguela Current : cools the Western Cape of S. Africa vineyards
Humboldt Current : cools Western Chile
Jet Stream : brings warmer wet air to European vineyards

Question 8

How can fog help grape growing? Example?

Answer 8

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.

Question 9

What is the heat benefit of stony soils?

Answer 9

It can retain heat during the warnth of the day and release this into the vineyard in the evening to prolong ripening

Question 10

Which is better (for heat)? Dark or white soils?

Answer 10

Dark soils absorb heat better and can be critical in cooler climates.

Question 11

What is meant by Aspect?

Answer 11

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.

Question 12

Define Continentality.

Answer 12

It is the difference in temperature between the hottest and coldest months in the year ie height of summer, depths of winter

Question 13

What temperature range does a region with high continentality experience?

Answer 13

High continentality means the region will experience a LARGE DIFFERENCE in seasonal temperatures.

Question 14

What temperature range does a region with low continentality experience?

Answer 14

Low continentality means the region will experience a SMALLER DIFFERENCE in seasonal temperatures.

Question 15

What does continentality determine for the grape grower?

Answer 15

a) the length of the growing season and total amount of heat available;
b) which grape varieties can be successfully grown.

Question 16

Why might a region near a large body of water have a different continentality than an inland region?

Answer 16

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.

Question 17

What is DIURNAL RANGE.

Answer 17

The difference between daytime and nighttime temperatures.

Question 18

What impact does cool/ warm nights have on grape ripening?

Answer 18

Cool - help slow the loss of acidity and aromas in the grapes.
Warm - accelerate ripening

Question 19

What factors can impact the diurnal range?

Answer 19

a) Proximity to lakes, seas and rivers

b) Cloud cover

Question 20

What impact might proximity to water mass have on heat?

Answer 20

a) Proximity to lakes, seas and rivers - reflected heat overnight/ cooling breeze

Question 21

What impact might cloud cover have on diurnal range?

Answer 21

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

Question 22

Which part of the vine is most at risk from winter freeze? What can mitigate this?

Answer 22

The graft area. Earthing up can be used.

Question 23

What impact might mild/ no winter have on the vine?

Answer 23

a) no dormant period so may overproduce - shortens life, quality diminished;
b) pests can survive and attack vines the following summer.

Question 24

What impact might spring frosts have on the vine?

Answer 24

Can kill new budburst and young shoots. Enormous impact on yields

Question 25

What are the four main methods of combatting frost?

Answer 25

Heaters
Wind machines
Sprinklers
Vineyard design

Question 26

How do heaters combat frost? (Bougies/chaufferettes)

Answer 26

Heat generated causes air movement preventing cold air from settling

Question 27

How do wind machines combat frost?

Answer 27

They draw warmer air from above to keep temp at ground level above freezing. May have a heater

Question 28

How do sprinklers combat frost?

Answer 28

They spray water which, as it freezes releases heat into the plant tissue protecting buds and shoots (Aspersion)

Question 29

How can vineyard design minimise risk of frost?

Answer 29

Planting on slopes avoids depressions into which cold air sinks. Middle of slope is best.
Vines can be trained to grow high to avoid theworst of the cold air.

Question 30

What two temperature hazards are possible during the growing season?

Answer 30

Excess cold and excess heat

Question 31

What impact can excess cold have?

Answer 31

In spring it can delay budburst which shortens the growing season and the time available for ripening. It can also disrupt fruit set meaning a smaller than normal crop of grapes.

Question 32

What impact can excess hot temperatures have?

Answer 32

In prolonged periods of extreme heat the vine activity will slow and eventually stop. Block sugar production which prevents grapes from ripening properly and in extreme cases vine may die.