The shoots (March/April)
The beginning of spring marks the end of the grapevine’s rest. The vegetative cycle starts with the grapevine’s “cry”, i.e., with the loss of sap through the cuts made during winter pruning. This phenomenon precedes budding or bud burst, which usually takes place 3 to 5 weeks afterwards.
Budding depends on the grapevine’s location, so not all vines start their vegetative cycle at the same time. Usually, the first shoots need medium temperatures – around 12ºC – to start “crying”. On the other hand, if the grapevine’s vegetative cycle starts too early, there’s a higher risk of suffering from spring frosts.
The leaves (April/May)
After the shoots and leaves are born, the grapevine has flower buds. At this stage, frosts are the grapevine’s worst enemy. Currently, one can predict with some clarity the most critical times of the year on a meteorological level.
The flowers and fruits (May/June)
Flowering lasts for about ten days and is characterised by the expansion of the rachis of inflorescences and by the opening of the flowers. Fertilisation occurs almost at the same time as flowering.
Not all fertilised flowers will become grape berries, since the flowers may drop from the plant (blossom drop) or due to imperfect fertilisation, which produces very small berries without seeds and hard to mature (called millerandage). After fertilisation, the ‘normal’ berries start to mature.
During maturation, the berries grow in size and change their chemical composition. In a first stage the green, small, hard berries increase their size and change their colour to golden or redish tones. Later, chemical transformations occur, namely the balance of the berries acidity. At this stage, the main threats to the vine are rot and downy mildew.
Ripening is the stage that precedes harvest and allows the grapes to reach optimum sugar levels for the production of wine. In red grape varieties, ripening also enables colouring and tannins appropriate for winemaking. The ripening time varies according to the climatic conditions, the characteristics of the grapevine and the producer’s intentions. Some grapes benefit from fast ripening, while others get unique aromas and sugars when they stay in the grapevine for longer periods.