The Vine Growth Cycle Flashcards
Explain dormancy in a vine
Average air temperatures below 10°C (50°F) are too cold for the vine to grow and therefore in winter the vine is dormant. Winter dormancy typically starts with leaf fall in the autumn and ends with budburst in the spring. Without leaves, the vine cannot photosynthesise. Therefore, until it has grown new leaves, the vine supports its growth by using stores of carbohydrates, mostly starch, accumulated during the previous growing season in the roots, trunk and branches.
What happens to a vine if temperatures get below -15 c?
Vines can be severely damaged or killed by temperatures below −15°C (5°F). Temperatures below −25°C (−13°F) will kill most V. vinifera.
During which months does dormancy occur?
November–March in the Northern Hemisphere, May–September in the Southern Hemisphere
What factors effect the timing of budburst/budbreak?
Air Temperature
Soil Temperature
Grape Variety
Human Factors
Explain how air temperature effects budburst/budbreak?
For buds to burst, sufficiently high temperatures are needed (average air temperature approximately 10°C / 50°F). Compound buds therefore generally remain dormant over winter and burst when temperatures rise in the spring.
Explain how soil temperature effects budburst/budbreak?
Higher soil temperatures around the roots encourage earlier budburst. Dry, free-draining soils, such as sandy soils, tend to warm up more quickly than water-storing soils, such as clay-rich soils, and therefore can be advantageous in cool climates where an early start to the growing season improves the chance of ripening.
Explain how grape variety effects budburst/budbreak?
Average temperature required for budburst depends on grape variety. Grape varieties that require relatively low temperatures at budburst are referred to as ‘early budding’. They include Chardonnay, Pinot Noir, Merlot and Grenache. Grape varieties that require higher temperatures are referred to as ‘late budding’ and include Sauvignon Blanc, Cabernet Sauvignon and Syrah. Because the buds of late-budding varieties need higher temperatures to burst, they are less at risk of spring frosts.
Explain how human factors effects budburst/budbreak?
Some viticultural practices can also advance or delay budburst. For example, carrying out winter pruning late in the dormant period can postpone budburst, and this technique can be used in areas where spring frost is a known problem.
What effect does continental or maritime climate have on budburst/budbreak?
Continental-rapidly increasing temperatures in the spring means that budburst can be relatively uniform and this has positive implications for the homogeneity of later stages in the growing season, potentially eventually leading to a crop of grapes with even ripeness.
Maritime-less contrast between winter and spring temperatures, budburst can be less synchronised. Furthermore, problems can occur when a few unusually mild winter days cause early budburst as any cold days and frosts that follow can potentially harm the newly burst buds, leading to lower yields.
During which months does budburst/budbreak occur?
March–April in the Northern Hemisphere, September–October in the Southern Hemisphere.
What does the vine need during shoot and leaf growth?
Stored carbohydrates, Warmth, Sunlight, Nutrients and water
How can shoot growth be negatively effected?
If carbohydrate levels are low (for example, caused by excessive leaf removal, water stress, mildew infections or high crop loads in the previous growing season) or water stress.
During which months do shoot and leaf growth occur?
March–July in the Northern Hemisphere, September–January in the Southern Hemisphere
During which months do flowering and fruit set occur?
May–June in the Northern Hemisphere, November–December in the Southern Hemisphere
Explain prompt buds and compound buds
Prompt buds will burst within the growing season producing new shoots called lateral shoots. Compound buds will remain dormant until the following spring and provide the shoots for next year.
