The vine growth cycle Flashcards
The 7 stages of the vine growth cycle
- Dormancy
- Budburst
- Shoot and leaf growth
- Flowering and fruitset
- Grape development
- Harvest
- Leaf fall and dormancy
Dormancy
November-March (NH)
Average air temp below 10 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 budburlt in the spring.
Without leaves the vine cannot photosynthesis. Therefore, until it has grown new leaves, the vine supports its growth by using stores of carbohydrates accumulated during the pervious growing season in the roots and turn.
Extreme lows in temp, such as those found in the winter in Canada, New York State and China, can be harmful to the vine even when it is dormant. Vines can be damaged or killed by temp below -15. Temp below -25 will kill most V. vinifera.
Winter pruning is carried out during this dormant period.
There are vineyard management techniques that can be used to protect the vine in areas of winter freeze.
Budburst
Budburst marks the end of winter dormancy. In this process buds swell and open, and green shoots start to emerge.
The timing of budburst depends on a number of factors:
- Air temperature
- Soil temperature
- Grape variety
- Human factors
Budburst - Air temperature
For buds to burst (compound buds formed in the pervious growing season), sufficiently high temperatures are needed (10)
Regions that have marked differences between the various seasons (continental climates) can be advantageous for successful budbust. In these places the rapidly increasing temperatures in the spring mean that budburst can be relatively uniform and this has positive implications for the homogeneity of later stages in the growing season, potentially even leading to a crop of grapes with even ripeness.
In regions where there is often less contrast between winter and spring temperatures (maritime climates), bud burst can be less synchronized. Problems can occur when a few usually mild winter days cause early budburst; any cold days ad frosts that follow can potentially harm the newly burst buds, leading to lower yields.
Budburst - Soil temperatures
Higher soil temperatures around the roots encourage early bud burst.
Dry, free draining soils, such as sandy soils, tend to warm up more quickly than water-storing soils, such as rich clay soils, and therefore can be advantageous in cool climates where an early start to the growing season improves the chance of ripening.
Budburst - Grape variety
The average temperature required for budburst depends on the variety.
Merlot vines open at temperatures slightly lower than 10, Ugni Banc buds open at temperatures slightly higher than 10.
Varieties that require relatively low temperatures to burst are referred to as ‘early budding’ varieties (Chardonnay, Pinot Noir, Merlot and Grenache).
Varieties that require higher temperatures are referred to as ‘late budding’ varieties (Sauvignon Blanc, Cabernet Sauvignon and Syrah). Because they need higher temperatures to burst they are less at risk of spring frost.
Early budding is not necessarily also early ripening. For example Grenache buds early and ripens late.
Budburst - Human factors
Some viticultural practices can advance or delay budburst.
Carrying out winter pruning late in the dormant period can postpone budburst, can ben used in areas where spring frost is a known problem.
Shoot and leaf growth
March-July
During spring and early summer shoots continue tor grown, and leaves and inflorescences mature.
Carbohydrates stored in the roots, trunk and branches support the initial shoot growth. If carbohydrate levels are low (excessive leaf removal, water stress, mildew infections, or high crop loads in the previous growing season), shoot growth can be negatively effected.
As leaves develop and mature they provide further growth via photosynthesis, and therefore need warmth and sunlight for this to take place.
As the vine grows, so does the vine’s need for nutrients. It is important that vines do not suffer from water stress in this time as thins can limit photosynthesis and shoot growth. Nutrients uptake through the roots is also impaired in very dry soils.
Water stress –> Stunted shoot growth –> Poor quality
Stunted shoot growth can lead to small, weak shoots and a reduction in leaf number or smaller leaves. Inflorescences that do not flower properly and/or grape bunches that do not ripen fully. This can lead to poor fruit quality and lower yields.
Describe the process of Flowering and fruit set
Describe flowering
Describe fruitset
Describe the process (5 steps)
May-June
Yield and quality of grapes is the current growing season are strongly influenced by the processes of flowering and fruit set.
Flowering describes the opening of the individual flowers within an inflorescence. Fruit set is therm used to describe the transition from flower to grape.
- Within this process the pollen-laden stamens (anther/filament) are exposed.
- The pollen grains are shed and land on the moistened stigma surface, a process called pollination.
- Then the pollen grain germinates, and each pollen grain produces a pollen tube.
- The pollen tubes penetrate the stigma and then the ovule (female reproductive cells) in the ovary. Then the pollen tube delivers the sperm cells, which fertilizes the eggs in the ovule. Leading to the formation of a grape berry.
- The fertilized ovules form seeds, up to four per grape. The wall of the very enlarges to form. the skins and pulp of the grape.
Describe bud fruitfulness
Bud fruitfulness describes the number of inflorescences that will develop from a bud in the next growing season and is strongly influenced by the conditions during flowering and fruit set of the current growing season.
The compound buds will stay dormant until the following spring and provide the shoots of next year. Shading compound buds, low temperatures under 25, water stress and nutrient deficiency can all limit bud fruitfulness.
Conditions for successful flowering
Flowering typically takes place within 8 weeks of bud burst. However, timing extremely depend on temperature.
Enough sunlight, warmth, water, nutrients during this part of the growing season are essential for bud fruitfulness in the next growing season
Warm conditions lead to earlier flowering, min temperatures of 17 are favorable for successful flowering. With such temperatures, an individual inflorescence can flower in a few days.
Low temperatures can lengthen duration of flowering, with weeks passing between the earliest and latest flowering. Which can negatively effect the evens of ripening.
Conditions for successful fruit set
Typically, 30% of flowers will become grapes, but this can range from 0% to 60%.
Pollen germination requires warm temperatures (optimal 26-32).
Pollen tube growth is negatively affected by cold, rainy and/or windy conditions and can lead to irregular fruit set, which also have a negative effect, leading to reduced yields.
Two common forms of irregular fruits set are:
- Coulore
- Millerandage
Coulore
A condition of the grape bunch in which fruit set has failed for a high proportion of flowers. Occurs when ovule fertilization is unsuccessful, and therefore no grape develops. Excessive coulore can reduce yield dramatically.
Caused by an imbalance in carbohydrate levels, this can result from low rates of photosynthesis, which may be caused by cold, cloudy conditions or hot, arid conditions with high water stress.
It can also result from vigorous shoot growth diverting carbohydrates from the inflorescence. Very fertile soils, have application of fertilizers and vigorous rootstocks can all cause strong shoot growth and therefore lead to coulore.
Grenache, Cabernet Sauvignon, Merlot and Malbec are more susceptible to coulore than others.
Millerandage
A condition of the grape berry in which there is a high proportion of seedless grapes. They can still ripen normally, but are smaller than grapes with seeds and 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.
Millerandage can result from cold, wet, windy weather at pollination and fruit set.
Chardonnay and Merlot are more susceptible than others.
4 stages of grape development
June-October
Stage 1: Grape berry formation
Stage 2: Veraison
Stage 3: Ripening
Stage 4: Extra ripening
