Vine Growth Cycle Flashcards
What time of the year do vines go in to dormancy?
Northern Hemisphere: November - March
Southern Hemisphere: May - September
Why does dormancy occur?
Average air temperatures below 10°C (50°F) are too cold for the vine to grow and therefore in winter the vine is dormant.
How does the vine support itself during dormancy?
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 low temperatures are damaging to wines?
- Temperatures below −15°C (5°F).
- Temperatures below −25°C (−13°F) will kill most vines.
- Problematic during Winter in Canada, New York State and China
Which important vineyard activity is done during dormancy?
Winter Pruning
What is another word for budburst?
Budbreak
What is budburst?
When vine buds swell and open, and green shoots start to emerge.
What are four factors that determine when budburst occurs?
- Air Temperature
- Soil Temperature
- Grape Variety
- Human Factors (e.g. late winter pruning)
What are the temperature requirements for a bud to burst?
Average of 10°C / 50°F
Why can regions with continental climates be advantageous for successful budburst?
Rapidly increasing temperatures in the spring mean that budburst can be relatively uniform.
This has positive implications for the uniformity of later stages in the growing season, leading to a crop of grapes with even ripeness.
Why can regions with maritime climates be disadvantageous for budburst?
Budburst can be less synchronised and uneven.
Problems can occur when a few unusually mild winter days cause early budburst; any cold days and frosts that follow can potentially harm the newly burst buds, leading to lower yields.
How can soil temperatures encourage earlier budburst?
Higher soil temperatures around the roots encourage earlier budburst.
What types of soils are beneficial in cooler climates?
Dry, free-draining soils (e.g sandy soils) tend to warm up more quickly than water-storing soils (e.g. clay-rich soil). This is advantageous in cool climates where an early start to the growing season improves the chance of ripening.
What is meant by an ‘early budding’ grape variety?
Grape varieties that require relatively low temperatures at budburst.
Name three late budding grape varieties.
Cabernet Sauvignon
Sauvignon Blanc
Syrah
Name four early budding grape varieties.
Chardonnay
Pinot Noir
Grenache
Merlot
Is budding time linked to ripening time?
No, e.g. Grenache buds early and ripens late.
What human factors can influence budburst?
Carrying out winter pruning later can delay budburst. This is useful in areas prone to spring frost.
When is budburst in the Northern Hemisphere?
March - April
When is Budburst in the Southern Hemisphere?
September - October
When do shoots and leaves grow, in the Northern Hemisphere?
March to July
When do shoots and leaves grow, in the Southern Hemisphere?
September to January
What is Shoot and Leaf Growth?
When the shoots continue to grow, and leaves and inflorescences (a cluster of flowers on a stem) mature.
At what stage does the fastest rate of shoot and leaf growth occur?
The fastest rate of growth generally occurs between budburst and flowering.
What initially supports shoot growth?
Carbohydrates stored in the roots, trunk and branches of the vine support the initial shoot growth.
What supports shoot growth later in the growing season?
As leaves develop and mature, they provide energy for further growth via photosynthesis, and therefore need adequate warmth and sunlight for this to take place.
What four factors might contribute to low carbohydrate levels?
Excessive leaf removal
Water stress
Mildew infections
High crop loads in the previous growing season
What main problem can occur during shoot and leaf growth?
Water Stress
- can limit photosynthesis and shoot growth
- can limit nutrient uptake through the roots
What does stunted shoot growth lead to?
- Small, weak shoots
- A reduction in leaf number or smaller leaves
- Inflorescences that do not flower properly
- Grape bunches that do not ripen fully
- Poor quality
- Lower yields
What does a vine need during the shoot and leaf growth stage?
Stored Carbohydrates
Warmth
Sunlight
Nutrients
Water
Nutrients: Phosphorus, Potassium, Nitrogen
When is Flowering and Fruit Set in the Northern Hemisphere?
May - June
When is Flowering and Fruit Set in the Southern Hemisphere?
November-December
What happens to buds during Flowering and Fruit Set?
- New buds develop at the base of the leaf stalks (petioles) on the new growing shoots
- 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.
(flowering and fruit set)
What buds form and when do they burst?
- 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
(flowering and fruit set)
What four factors can limit bud fruitfulness (the number of inflorescences that will develop from a bud) in the next growing season?
- Shading of compound buds
- Temperatures that are too low (under 25°C / 77°F)
- Water stress
- Nutrient deficiency
(flowering and fruit set)
Why is the flowering and fruit set period important for the next year’s yield?
- Shading of compound buds, temperatures that are too low (under 25°C / 77°F), water stress and nutrient deficiency can all limit bud fruitfulness (the number of inflorescences that will develop from a bud) in the next growing
- Each inflorescence will become a bunch of grapes next year
(flowering and fruit set)
Define Flowering.
Flowering describes the opening of the individual flowers within an inflorescence.
(flowering and fruit set)
Define Fruit Set.
Fruit set is the term used to describe this transition from flower to grape.
How does a flower become a grape?
- The pollen-laden stamens (consisting of an anther and filament) are exposed.
- The pollen grains are shed and land on the moistened stigma surface, a process called pollination. Here, they germinate, with each pollen grain producing a pollen tube.
- These pollen tubes penetrate the stigma and then the ovule (the female reproductive cells) in the ovary.
- The pollen tube delivers the sperm cells, which fertilise the eggs in the ovule. This leads to the formation of a grape berry.
- The fertilised ovules form seeds, with up to four per grape.
- The wall of the ovary enlarges to form the skin and pulp of the grape.
How are vines typically pollinated?
Cultivated varieties of vines are normally self-pollinating (the pollen from the stamens of one flower is transferred to the stigma of the same flower, or a different flower in the same plant).
What conditions are needed for successful flowering?
Warm conditions (minimum temperature of 17°C / 63°F)
What condition is not ideal for successful flowering? Why?
Low temperatures
- Can lengthen the duration of flowering, with weeks passing between the earliest and latest flowering
- Uneven ripening
How long after budburst does flowering typically occur?
Flowering typically takes place within eight weeks of budburst.
What conditions are needed for successful fruit set?
Pollen germination requires warm temperatures (optimal at 26-32°C / 79-90°F).
What percentage of flowers become grapes?
- Typically, 30%
- Can range from 0-60%
What conditions are not ideal for successful fruit set?
Cold, rainy and/or windy conditions:
- Pollen tube growth negatively affected
- Irregular fruit set
- Key cause of poor yields in cool climates
Hot, dry, windy conditions
- Water stress
- Reduced yields
What are the two common forms of irregular fruit set?
- Coulure
- Millerandage
What is Coulure? Is it normal?
- A condition of the grape bunch in which fruit set has failed for a high proportion of flowers.
- Some coulure is normal.
- However, excessive coulure can reduce yield dramatically.
Which four grape varieties are more susceptive to coulure?
- Grenache
- Cabernet Sauvignon
- Merlot
- Malbec
What causes Coulure?
Coulure is caused by an imbalance in carbohydrate levels.
– Cold, cloudy conditions
– Hot, arid conditions with high water stress
— Vigorous shoot growth diverting carbohydrates from the inflorescence.
– Very fertile soils
– Heavy application of fertilisers
– Vigorous rootstocks
What is Millerandage?
- A condition of the grape bunch in which there is a high proportion of seedless grapes.
- The seedless grapes can still ripen normally, but are smaller than grapes with seeds.
- Millerandage may therefore reduce the volume of wine that can be produced.
- Some seedless grapes stay small, green and unripe, which can be negative for wine quality.
Which grape varieties are more susceptible to Millerandage?
Chardonnay
Merlot
What causes Millerandage?
Millerandage can result from cold, wet, windy weather at pollination and fruit set
When is Grape Development in the Northern Hemisphere?
June - October
When is Grape Development in the Southern Hemisphere?
December to April
What are the four stages of grape development?
- Grape Berry Formation
- Veraison
- Ripening
- Extra-Ripening
What happens during grape berry formation?
- Hard green grapes start to grow in size
- Tartaric and malic acids accumulate
- Some aroma compounds and aroma precursors accumulate
- Tannins accumulate (very bitter)
- Sugar levels are low throughout this stage.
- Water flow into the grape is high at this stage (trough the XYLEM, channel from the roots to the rest of the plant)
What are methoxypyrazines?
Methoxypyrazines are aroma compounds that contribute to herbaceous aromas/flavours in some wines, such as those made from Sauvignon Blanc, Cabernet Sauvignon and Cabernet Franc. They develop during grape berry formation.
What causes a prolonged grape berry development period?
Too much water and nitrogen
- Encourage shoot growth in preference to grape ripening
- Causes delay in the onset of the ripening stage
- May not be sufficient time for ripening before the weather becomes cold and rainy and the grapes need to be harvested
What speeds up the grape berry development period and how does this effect the final wine?
Mild water stress
- Leads to smaller grapes
- Reduces juice yield
- Greater skin to pulp ratio (can be associated with better quality in red wines
- higher levels of colour, tannins and aroma compounds)
What occurs during Veraison?
Grape growth slows down (lag phase)
- Grape cell walls become stretchy and supple
- Green-coloured chlorophyll in skin cells is broken down
- Grapes of black varieties start to become red in colour due to the synthesis of compounds called anthocyanins
Synthesis = construction of complex compounds from simpler ones
What does the vine need during grape development?
- Sunlight
- Warmth
- Mild water stress
What are adverse conditions during grape development?
- Too much water and nutrients
- Excessive shading of grapes
- Very cold or very hot conditions throughout the day and night
When does shoot growth start to slow down?
Ripening
What happens to the grape during ripening?
- The cells in the grape expand rapidly
- Sugar and water accumulate
- Acid levels fall
- Tannins, colour and a number of aroma precursors and aroma compounds develop
(Grape ripening)
What is the temperature required for Photosynthesis to occur at the maximum rate?
18-33°C (64-91°F)
What effect do warmer years with very hot, dry conditions have on the vine and on photosynthesis?
Extreme water stress
- Cause photosynthesis to slow or stop
- Hinder sugar accumulation
How do the grapes develop sugar?
- Sugar is produced in the vines’ leaves by photosynthesis
- A sugar solution is transported by the phloem into the grapes
movement of sugar solution = GRAPE TRANSPIRATION
In what conditions is the rate of grape transpiration faster? In what conditions is it slower?
Faster = warm, dry conditions
Slower = cool, humid conditions
How does the concentration of tartaric acid change during ripening?
- Total amount of tartaric acid in the grape generally does not change
- However concentration falls during ripening due to dilution, as sugar and water accumulate in the grape
Why do wines from cooler climates tend to have higher natural acidity?
- Malic acid can be metabolised in respiration during the ripening stage (used to produce energy)
- Respiration is slower at cool temperatures than warm ones
- Cool night time temperatures also mean that less malic acid is lost during respiration
During the final month of ripening, what temperature range is crucial?
- 15 - 21 degrees C (59 - 70 degrees F)
- Warmer than 21: rapid loss of acidity (and rise of PH)
- Cooler than 15: acidity levels are too high (due to reced loss of acidity by respiration)
What happens to methoxypyrazine levels during ripening?
- Levels fall
- Cool temperatures and limited sunlight (e.g. due to excessive shading of bunches) can hinder this decrease and the resulting wines may show particularly herbaceous aromas/flavours
What aroma compound increases during ripening? What flavours can they create?
- Terpenes
- Give floral and citrus aromas such as the grapey aromas found in Muscat
What conditions give off ‘riper’ aromas?
Warmer, sunnier climates tend to produce grapes and wines with aromas that could be described as ‘riper’ than cooler, less sunny climates.
In black grapes, when are tannin levels the highest?
- Highest at Verasion
- Start to decrease slightly at ripening
When tannins polymerise, how does it affect the flavor?
Become less bitter
What happens to anthocyanin during ripening? What factors encourage this?
- Anthocyanins increase during the ripening stage
- Plentiful sunlight
- Temperatures between 15°C and 25°C
What 4 factors determine length of ripening?
- Grape Variety
- Climactic Conditions
- Management of the Vine & Vineyard
- Time of Harvest
Name 2 early ripening grape varieties.
- Chardonnay
- Pinot Noir
Name 2 late ripening grape varieties.
- Cabernet Sauvignon
- Grenache
In what climactic conditions is sugar ripening quickest?
- Sugar ripening is quickest in warm, dry conditions.
- However, very hot or dry conditions can cause the vine to shut down, which inhibits grape formation and ripening.
Name 2 elements of vineyard management that can slow down ripening.
- Heavy crop loads
- Excessive shading within the vine canopy
What happens if ripe grapes are left on the vine?
- Grapes start to shrivel
- No more sugar or water are imported to the grape by the phloem at this stage, but water loss in the grape through grape transpiration means that sugars are concentrated.
- Extra-ripe aromas can also develop in this stage
What are the factors that determine ripeness?
- Amount of sugar in the grapes
- Level of acidity in the grapes
- Flavour Profile
- Tannin Ripeness
Describe tannins during grape formation and ripening.
- During grape formation, skin tannins accumulate but are bitter to taste.
- During ripening, tannins polymerise and become less bitter.
What is a winemaker’s main concern with tannins?
- Avoid bitter unripe tannins
Why do wines from warm climates tend to have higher levels of alcohol?
The desired sugar ripeness may be reached before the desired ripeness of aromas and tannins.
What can winemakers do if the optimal balance of sugar, acid and tannins isn’t achieved naturally?
Make adjustments during the winemaking process.
What’s easiest to adjust: sugar, alcohol, acid, or tannin levels? What does this mean when grape growers try to find optimal ripeness?
- Sugar, alcohol, acid is easier to adjust than bitter, unripe tannins
- Many grape growers will focus on attaining the desired level of tannin and aroma ripeness first since they can adjust the other things
What happens to the vines in late summer and autumn?
Late Summer
- Cane Formation: green shoots lignify (become woody and rigid) Autumn
- Leaves fall
- Carbohydrate reserves stored in the roots, trunk, branches
- Vine enters its dormant period
