Vine Growth Cycle Flashcards
Vine Growth Cycle
Dormancy Budburst Shoot and Leaf Growth Flowering and Fruit Set Grape Development Harvest Leaf Fall and Dormancy
Dormancy
Nov - March / May - Sept Vines cannot grow in <10C temps Starts with leaf fall in autumn and ends with budburst in spring As it cannot photosynthesize it sustains itself by using stores of carbohydrates (starch) in the root, trunk, branches. Below -20C and severely damage or kill a vine; Below -25C will kill unless precautions. Winter pruning occurs
Budburst
March - April / Sept - Oct Buds swell, open, and shoots begin to emerge Impacted by: Air Temperature: Need avg air temp of 10C. Continental climates can be advantageous as the rapid increase in temp in spring results in uniform burst. Maritime can be less. Unusually mild days can cause early burst and then cold or frost can damage. Soil Temp: Higher temps encourage burst. Dry free draining (sandy) warm up quicker than water storing (clay). Variety: Avg temp needed is variety dependent. Merlot, Chard, Pinot Noir, Grenache need lower than 10C and are early budding. Cab Sauv, Sauv Blanc, Syrah need higher and are late budding. Human: Later winter pruning can delay
Shoot and Leaf Growth
March - July / Sept - Jan Shoots and leaves grow and inflorescences mature. Fastest rate of growth b/n budburst and flowering Vigor is vegetative growth (shoots, leaves, lateral shoots) and has implications on yield and ripening. Vines with high vigor grow long shoots, large leaves, lateral shoots. Depends on natural resources, planting material (clone, root, variety), and disease presence. Carbohydrates stored support initial shoot growth and if low can negatively impact. As leaves develop they provide energy through photosynthesis and need warmth and light for this. As vine grows so does need for nutrients (nitrogen, potassium, phosphorous). Water stress at this time would limit shoot and leaf growth
Flowering and Fruit Set
May - Jun / Nov - Dec
New buds develop at the base of petioles. Prompt burst in the same year producing lateral shoots. Compound remain dormant till folowing year and provide shoots for next year.
Shading of compound buds, temps too low (<25C), water stress, nutrient deficiency can limit bud fruitfulness (number of inflorescences that will develop from a bud) in the next year. Hence conditions this time of year can significantly impact next year. Riesling can be fruitful in cooler years.
Yield of current year sig influenced by flowering and fruit set. Flowering is opening of individual flowers on inflorescence. The pollen laden stamens (anther and anther filament) are exposed. Pollen grains are shed and land on moistened stigma (pollination). They germinate and each grain produces a pollen tube. Tubes peentrate stigma then the ovule in the ovary. Delivers sperm cells that fertilize eggs in the ovule.
Forms a grape berry with up to four seeds. Walls of the ovary enlarge to form the skin and pulp. Fruit set is this transition from flower to grape. Cultivated varieties are normally self-pollinating
Vine Anatomy
Conditions for successful flowering
Typically within 8 weeks of budburst but very temperature dependent
Warm conditions lead to earlier flowering.
Min 17C needed for successful flowering. At these temps an individual inflorescence can start and finish flowering within a few days.
Lower temps lengthen duration with weeks passing in b/n start and finish. This has a negative impact on evenness of ripening
Conditions for successful fruit set
Only about 30% of flowers become grapes, but can range from 0% to 60%
Pollen germination requires 26 - 32C.
Pollen tube growth is negatively impacted by cold, rainy and/or windy conditions and this can result in irregular fruit set and is a key cause of poor yields in cool climates.
Hot, dry, windy condittions leading to water stress can also negatively impact.
Types of Irregular Fruit Set
Coulure: Where fruit set has failed for a high number of flowers. Occurs when ovule fertilization is unsuccessful and no grape develops. Some coulure is normal but excessive reduces yields.
Caused by imbalance in carbohydrate levels. Can resuls from low levels of photosynthesis (cold cloudy or hot arid with water stress). Or vigorous shoot growth deiverting carbs from inflorescences (very fertile soils, fertilizer, vigorous rootstocks). Grenache, Cab Sauv, Merlot, Malbec very susceptible.
Millerendage: A condition where there is a high number of seedless grapes in a bunch. They ripen normally but are smaller so may reduce yield. Some seedless grapes stay small, green, unripe whch can impact quality.
Results from cold wet windy weather at fruit set with Chard, Merlot more susceptible
Grape Development
Jun - Oct / Dec - Apr
Stage 1 Early Grape Growth: Hard green grapes start to grow and tartaric and malic acid accumulate. Some aroma compounds and precursors develop (methoxypyrazines). Tannins accumulate and are very bitter. Sugar levels are low. Water flow to the grape by xylem is high.
Too much water and nutrients can prolong this stage as it encourages shoot growth instead of grape ripening. This may delay the onset of ripening and then not have enough time. Mild water stress can speed up leading to smaller grapes which may be desirable in red wine production.
Stage 2 Veraison: Grape growth slows down for a few days (lag phase). Grape cells become more stretchy and supple, chlorophyl in skin is broken down and black grapes turn red as anthocyanins are synthesized.
Grape Ripening
Stage 3 Ripening: Most important part for grape quality. Shoot growth has slowed substantially. Grape cells expand rapidly, sugar and water accumulate, acid levels fall. Tannins, color, aroma compounds and precursors develop. Harvest marks the end.
Sugar accumulates quickly at beginning then slows. Produced via photosynthesis which is at its max b/n 18 - 33C and sunshine above 1/3 full sunshine. Too cold or cloudy or too hot and dry can hinder. Water flow via xylem slows and sugar is transported by phloem. Sugar accumulation related to grape transpiration and is faster in warm dry climates. Can be too rapid if it’s too warm.
Amount of tartaric acid doesn’t change, but concentration does as sugar and water accumulate. Malic acid concentration falls faster as it is metabolized during respiration in this phase (before this it was sugar). Respiration is slower in cooler climates and hence higher acid.
Mean temps above 21C in the final month of ripening can lead to a rapid loss of acid (rise of pH). Below 15C can reduce acid loss to a point where grapes are too acidic. Cool night temps result in less malic acid loss. Hence higher diurnal ranges can have higher acid.
Methoxypyrazies levels fall but cool temps, limited sun (clouds or shade) can hinder and leave wines herbaceous. Other aroma compounds and precursors like terpenes develop.
In black grapes, tannins are high at veraison and decrease slightly throughout ripening. The tannins polymerize (process where small molecules combine chemically to produce a chain). This makes them less bitter. Sunshine promotes more tannins pre-veraison and greater polymerization post veraison.
Anthocyanins increase at this stage, most rapidly with plentiful sunlight and temps b/n 15 - 25C.
Lenght of Ripening Stage
Grape Variety: Some varieties ripen earlier (Char, Pinot) others later (Cab Sauv, Grenache). Zinfandel is prone to uneven ripening with some ripe and over ripe.
Climatic Conditions: Sugar accumulation is fastest in warm dry conditions. Very hot and dry can cause vine to shut down inhibiting ripening
Management of the vineyard: High yields, excessive shading, and actively growing shoots can slow ripening
Time of Harvest: Human factors (desired style, logistics) or natural (weather, disease)
Stage 4:
Extra Ripening: If grapes left on vine they begin to shrivel. No more sugar or water are imported to the grape by phloem but water loss occurs through grape transpiration. So sugars are concentrated.
Extra ripe aromas can develop, which may or may not be desirable. Grape shrivelling most likely in hot, sunny, dry climates. Some grapes more susceptible (Syrah).
Not always possible to leave on vine as weather and disease may pressure
Other changes in the vine
Late summer, green shoots lignify (become woody and rigid). Now described as canes.
In autumn leaves fall, carbohydrate reserves are laid down in roots, trunk, branches and vine enters dorman period.
