Viticulture 2 Flashcards
When does Verasion occur?
Veraison starts in late July in the Northern Hemisphere and in late January in the Southern Hemisphere.
Veraison is very much the tipping point in a grapevine’s annual lifecycle. It’s when the vine alters it’s focus from energy creation (through photosynthesis) to energy consumption where it concentrates its energy into making sweet grapes. The changing color (anthocyanin) and development of other polyphenols act as protectors to the grapes from sun, wind and other stresses. Following the onset of veraison, the ripening process then takes anywhere from 30–70 days for the grapes to become fully ready to make wine!
Vines change at Verasion……..
Before veraison, wine grapes are small, hard, highly acidic, and green-colored from the presence chlorophyll. When veraison commences, the vine starts to transport its energy stores from the roots into the grapes. The chlorophyll is replaced by anthocyanins (red grapes) or carotenoids (white grapes), sugars, and other nutrients. After veraison, the grapes begin to dramatically increase in size as they accumulate sugars (glucose and fructose measured in Brix) and start to develop aroma compounds. Also during this time, the acid levels begin to fall in the grapes. Acids continue to fall and sugars continue to rise until the grapes are perfectly in balance and ready to be harvested.
Cooler climates: winegrowers may choose to trim bunches from each vine in order to ensure the remaining bunches receive more nutrients and sugars from the roots.
Warmer climates: some growers may also choose to trim leaves off the vine to slow the rate of ripening and accumulation of sugars to delay ripening until later in the year when temperatures are cooler.
Certain Varieties Ripen Unevenly….
Some grape varieties have bunches that ripen very unevenly. Some will have ready and ripe berries on the same bunch as berries that are still green. Extreme uneven ripening is called millerandage and can produce wines that may smell sweet but that taste unbalanced, unripe or, “green.” Uneven ripening happens commonly in varieties like Pinot Noir, Sangiovese, Malbec, Gewürztraminer, and Zinfandel; this is why they’re considered some of the hardest grapes to grow in the business!
Shiraz Clone: 1654
The most widely planted clone in Australia. Small bunches, small berries, moderate yield. Generally a very stable clone, producing wines with power and deep colour.
Shiraz Clone: 470
A high quality French clone with loose clusters, botrytis resistance and low fruit weight per vine. High tendency to show rotundone.
Shiraz Clone: 2626
Widely planted, long bunches, tendency to show rotundone.
Shiraz Clone: SAVII17
Originally a Tahbilk selection. Perfumed, floral, pretty. Small berries, moderate yield, lots of colour. South Australian Vine Improvement Inc. (SAVII) important for colonial and source verification
Shiraz Clone: 1127
From the Harry Tillich selections and manurial trials conducted in the 1950s. Lighter yield than 1654. Floral, spice and dark fruit.
Shiraz Clone: PT23
Originally a Griffith clone from a set of pruning trials (PT). Widely planted, good for warm regions.
Shiraz Clones: Best’s Clone
From vines planted by Henry Best in 1866. Possibly not of Busby origin, rather from the Swiss near Geelong. Red fruits, purity and density.
