Bleeding – Budburst of the vineyard
Bleeding consider to be a natural pathway of a vine. It is the first sign of transition from dormancy to active growth which takes place approximately 15 days before budburst. The rise of the soil temperature (>10◦C at 25cm depth) enables the roots to become active. In general words, bleeding can be visible due to the fact that the vine releases liquids from pruning cuttings. Bleeding let the vine grower know that the plant is healthy for next season’s growth. Generally, lasts for two weeks, but can last for a month as well. Bleeding occurs on freshly pruned vines. The vines which pruned during autumn do not bleed so the vine grower must have that in mind.
Budburst occurs when the mean daily temperature reaches about 10◦C (variety dependant). There are 8 phenological stages of Budbreak which occurs in the vine (Scientific Approach):
1. Winter Bud
2. Bud Swell
3. Green Shoot Tip
4. Leaf Emergence
5. Leave Unfolded
6. Flower Clusters Visible
7. Flowers Clusters Separated
8. Flowers Separated
In terms of the factors affecting Budburst/Budbreak which differ from season to season can be the latitude/Altitude, Soil Type, Soil Humidity, Soil Colour, Moisture Content of Canes, Pruning System, Exposure to Sunlight, Hormones, Genetics (Variety), Air and Root Temperature, Position of the Bud on the spur/cane.
In some growing regions due to the extreme climatic conditions might be necessary for the vine to delay the process of budbreak/budburst. As mentioned above, the vine has the mechanism to start it’s growing phase when high temperatures occur. Some seasons early high temperatures might be followed from extreme low temperatures which might negatively affect the buds. So our job us vine growers and winemakers is to protect those vines in order to give us a high quality raw material by the end of the growing season. Some of the most effective techniques to achieve a delay on budburst are the late pruning during February and April. Regarding to articles those techniques of late pruning occurs in Ravaz. The addition of Iron Sulphate treatments at the end of winter can delay budburst for one or two weeks, but on the flipped site, the addition of this treatment during autumn showed opposite results on budbreak and budburst.
