The red leaves in the vineyard, between spectacle and concern.

It's the season when the leaves fall to the ground in one last shout of color. The vines give you a grand show. After a year of work, it's time for it to rest, but not before showing you how spectacular it is. Every year, in the fall, there is a certain feeling that the vines are dying. Falling leaves look like an orchestrated death, spectacular and brilliant.

Yellow, orange, purple, or brown leaves are spectacular for onlookers but worrisome for growers.

Why do some turn yellow and others turn red?

As the vines approach winter, the leaves begin to turn yellow. Chlorophyll, the substance that gives leaves their green appearance throughout the growing season from spring to fall and that converts light into energy during photosynthesis, begins to break down. Temperature, daylight, and weather events such as rain or drought cause the leaves to die in the fall, the chlorophyll breaks down and the yellow or orange auxiliary substances known as carotenes or carotenoids that have always existed in the leaves will now give them their color.

With the red ones, however, there is a different story. As some leaves die, anthocyanins (also found in the skin of the grapes) can combine with the remaining green pigments in chlorophyll, and then leaves display a multitude of shades of red. The red color in the leaves is specific to only a small number of grape varieties. How intense the shades of red depending on the variety the leaf belongs to, its inherent genetics, and the environment.

However, during this period, after the grapes have been harvested and are already being transformed into must and wine, the winegrowers begin a complicated process of identifying the vines that show leaves colored in shades of red, at varieties where this is not appropriate.

When the leaves turn red, it is an indication of a problem, a nutrient deficiency, or a disease caused by viruses, bacteria, or fungi. Because testing and managing a viral disease is very expensive, it is wiser to first rule out all other causes of red leaves: nutrient deficiencies, cold injury, and damage to root systems.

Anything that can cause blockage or stress in the vascular system that carries water and nutrients inside the plant, can develop red leaves.

It's an impressive sight to see the vines turn shades of red in the fall, but it's the plant's sign that it's suffering and a worrying sign for winegrowers. In cases of deficiencies, an aid with a mix of phosphorus, potassium, and magnesium helps the plant in the following year to eliminate deficiencies and stress. In the case of infection with viruses and bacteria, the only solution is to replace the infected vines.