The vine Flashcards
What are the two types of buds?
- Compound buds: Form one season, break on the next
- Prompt buds: Form and break open in one season; product lateral shoots
How can lateral shoots be helpful?
- Lateral shoots towards the end of main shoots can produce more leaves
How can lateral shoots be unhelpful?
- Lateral shoots not at the end of main shoots can impede airflow and shade fruit; can be removed in summer pruning
- Can produce fruit (“second crop”) that ripens later, and thus will be underripe if harvested with main crop (can be removed by green harvesting). Common with Pinot Noir.
What is one year old wood?
- Shoots from the previous growing season that weren’t removed, and that support compound buds that will release shoots for the growing season
What are the five basic stages of the vine growth cycle?
- Dormancy
- Budburst
- Shoot and leaf growth
- Flowering and fruit set
- Grape development
Dormancy:
* When does it happen (northern hemisphere)?
* What does the vine need during this stage?
* What are adverse conditions during this stage?
- November - March
- Temps below 10 C
- Extremely cold temps (-20 C can damage or kill, and -25 C will kill most)
Budburst:
* When does it happen (northern hemisphere)?
* What does the vine need during this stage?
* What are adverse conditions during this stage?
- March - April
- Average air and soil temps above 10 C
- Adverse: Frost, cold soils
What type of climate can have more uniform budburst? What is the consequence for grape ripeness?
- Continental, because rapid increase in temps means budburst happens quickly.
- Even budburst increases the likelihood of even ripening.
What soils can result in the best budburst in cool climates?
Free-draining, because they warm up more quickly than soils that retain water, which leads to quicker budburst in Spring.
What is an early budding variety, and what are some examples?
It buds slightly below 10 C. Examples:
* Chard
* Pinot Noir
* Merlot
* Grenache
What are some examples of late budding varieties?
- Sauv Blanc
- Cab Sauv
- Syrah
What can a vine grower do to delay budburst?
Do winter pruning late
Shoot and leaf growth:
* When does it happen (northern hemisphere)?
* What does the vine need during this stage?
* What are adverse conditions during this stage?
March - June
Needs:
* Stored carbohydrates
* Warm, sunlight, nutrients, water
Adverse:
* Low carbs (caused by conditions in prior growing season)
* Water stress (limit photosynthesis and nutrient uptake)
Flowering and fruit set:
* When does it happen (northern hemisphere)?
* What does the vine need during this stage?
* What are adverse conditions during this stage?
May - June
Needs:
* Warm temps (min 17 C) for flowering
* Sunlight on buds, warmth (above 25 C–though Riesling can tolerate cooler), water, and nutrients for bud fruitfulness next season
Adverse:
* Rainy
* Cloudy
* Windy
* Cold temps
What is flowering?
Opening of individual flowers within an inflorescence.
What happens if temps are below 17 C at flowering?
Lengthen duration of flowering, which has negative impact on evenness of grape ripening
What two types of conditions can interfere with fruit set?
- Cold
- Rainy
- Windy
(due to poor pollen tube growth)
or
* Hot
* Dry
* Windy
(due to water stress)
What is coulure, what are the three potential causes, and which varieties are esp susceptible?
Fruit set failure for a high proportion of flowers, caused by an imbalance in carbohydrate levels
Caused by:
* Cold, cloudy conditions
* Hot, arid conditions with high water stress (stopping photosynthesis)
* Vigorous shoot growth diverting carbs from inflorescence (perhaps by very fertile soils, excessive fertilizer, or vigorous rootstocks)
Grenache, Cabernet Sauvignon, Merlot and Malbec all very susceptible
What is millerandage, what causes it, and what varieties are more susceptible?
- High proportion of seedless grapes that are smaller (lower yield), some of which stay green and unripe (lower quality)
- Cold, wet, windy weather at fruit set
- Chard, Merlot
Grape development:
* When does it happen (northern hemisphere)?
* What does the vine need during this stage?
* What are adverse conditions during this stage?
June - Sept
Needs:
* Sunlight
* Warmth
* Mild water stress
Adverse:
* Too much water and nutrients (delays ripening)
* Excessive shading of grapes
* Very cold or very hot conditions throughout day and night
What are the four stages of grape development?
- Early grape growth
- Véraison
- Ripening
- Extra-ripening
What are five changes that happen to the grape in early grape growth?
- Acids: Tartaric and malic acids increase
- Methoxypyrazines (and some others) increase
- Tannins: Accumulate (promoted by sunshine), very bitter
- Sugar: Low
- Water: Flow into grape via xylem
What four things happen during véraison?
- Grape growth slows down for a few days (“lag phase”)
- Grape cell walls become more stretchy and supple
- Green-color chlorophyll in skin cells broken down
- Black varieties start to turn red due to synthesis of anthocyanins
What are the four general factors that determine the length of the ripening stage?
- Variety (early, late, or uneven)
- Climatic conditions
- Management of the vine and vineyard
- Time of harvest
What three climactic conditions are best for sugar accumulation and why?
- Max photosynthesis at temps 18-33 C
- Sunshine at least 1/3rd of full
- Warm, dry conditions speed grape transpiration, and therefore sugar transport into the grape
What conditions of the vine can slow down grape ripening?
- High yields
- Excessive shading of grapes by canopy
- Shoots still actively growing
What two categories of factors impact time of harvest?
- Human (wine style, logistics)
- Natural (weather (like rain), onset of disease)
What happens to acids post-veraison, and what factors impact this?
- Tartaric acid: Declines due to dilution by addition of water/sugar
- Malic acid: Also declines due to metabolization in respiration, which is quicker when warmer
- Mean temps above 21 C in the final month leads to rapid loss of acidity; mean temps below 15 C can reduce acid loss to unacceptable level (this is why high diurnal range can result in more acidic wines)
What impacts methoxypyrazine levels post-veraison?
- Cool temps and limited sunlight (due to excessive shade or cloud cover) can inhibit natural decrease
What happens to tannins in black grapes post-veraison, and what factors impact this?
- Decrease slightly
- Polymerize, which makes them less bitter
- Sunshine promotes polymerization
What happens during extra-ripening?
- Grapes lose water, which concentrates sugars (most likely in hot, dry, sunny climates)
- Extra-ripe aromas develop
What are the five most important nutrients for the vine?
- Nitrogen
- Potassium
- Phosphorus
- Calcium
- Magnesium
What are the effects of excessive and insufficient nitrogen?
Excess: too much vegetative growth (focus on shoots, too much shade, etc.)
Too little:
* Low vigor, yellowing of vine leaves
* Grapes with low nitrogen may give ferm problems
What are the effects of excessive and insufficient potassium?
Too much:
* Very high: Can cause problems with uptake of magnesium
* High: Can cause high potassium in grapes, linked to high PH
Too little:
* Low sugar accumulations
* Reduced yields
* Poor vine growth
What are the effects of insufficient phosphorus?
- poorly developed root system (thus problems taking up water and nutrients)
- reduced vine growth
- lower yields
What are the effects of insufficient calcium?
Rare, but has a negative influence on fruit set
What are the effects of insufficient magnesium?
- Reduced yields
- Poor ripening
What are the four natural factors that affect nutrient availability?
- Nutrients are transported in a water solution, so soil factors that impact water availability also impact nutrients (e.g., clay is better at holding nutrients)
- Soil pH. For example, iron is less available in high pH, leading to chlorosis. Phosphorus is less available in low pH soils.
- Organic nutrient compounds need to be broken down to inorganic compounds (via organisms that live in soil) to be available to vines
- Soil on slopes are often thinner and less fertile
What causes chlorosis, what does it look like, and what does it do?
- Iron deficiency, especially in high pH soils (like calcium carbonate such as limestone)
- Leaves turn yellow and photosynthesis stops
- Grape ripening and yields negatively impacted
What is soil texture? What soil is finely textured? What soil is loosely textured?
- The proportions of mineral particles of sand, silt, and clay
- Finely textured: high proportion of clay
- Loosely textured: high proportion of sand
What is loam?
Soil that has moderate proportions of clay, silt, and sand
What are the properties of finely textured soil?
- Effective at holding water and nutrients
- Hard for roots to penetrate and challenging for soil cultivation
What are the properties of loose textured soil?
- Poor at holding water and nutrients (i.e., free draining)
- Roots easily grow
What is soil structure? What does it determine?
- How the mineral particles form aggregates (crumbs)
- Size, shape, stability of aggregates determine water drainage, root growth, and workability of soil
What is humus and why is it good in soil?
- Organic matter formed by partial decomposition of plant and animal material by soil microbes and earthworms
- Spongey texture, large surface area, able to adsorb water and nutrients
- Helps bind soils together; helps retain water and nutrients
What does the suitability of soil for viticulture depend on?
- Texture and structure of soil
- How far the roots can penetrate (e.g., sandy soil may be fine if roots can extend over a large area)
- Climate (rain, heat, and light needed for the vine–e.g., free draining soils good for wet areas)
What are the WSET temp climate ranges?
- Cool: 16.5 C GST or below
- Moderate: 16.5 – 18.5 C
- Warm: 18.5 – 21 C
- Hot: above 21 C
What are the 5 benefits of grape exposure to sunlight?
a. Development of anthocyanins in black grapes
b. Reduced levels of methoxypyrazines
c. More tannins pre-véraison and more tannin polymerization post-véraison (less bitterness)
d. Increase in favorable aromas and precursors, like terpenes.
e. Warms grapes, which results in loss of malic acid
What is the potential negative about grape exposure to sunlight ?
Sunburn
How does lower latitude affect sunlight?
- more solar radiation per year on a parcel of land (due to angle and traveling through less atmosphere)
- less sunlight hours during growing season
All else being equal, what 5 characteristics will grapes at lower latitude tend to have?
(i) higher levels of sugar
(ii) lower levels of acidity
(iii) riper aromas
(iv) higher but riper tannins,
(v) more color intensity
What are the 3 primary impacts of altitude on temp and sunlight?
- Temps fall by about 0.6 C for every 100 m
- Sunshine more intense because it travels through less atmosphere and more UV radiation, both of which lead to anthocyanin and tannin synthesis.
- Often have high diurnal range, because there is less atmosphere to re-radiate heat back to the ground. Can be beneficial for retention of acidity.
What is the impact of an east-facing slope?
a. Morning sun, warming when air and soil temps are lowest
b. Especially in cool climates, can extend hours of vine growth and grape ripening
c. Dries out dew more quickly, reducing fungal disease
What is the impact of a west-facing slope?
a. Afternoon sun
b. In warm clients, perhaps too hot, with risk of sunburn (not an issue in Western Australian or California, where oceans are to the west)