Saturday 21 June 2025 at 04:42 (Italian time) the Summer solstice (in the northern hemisphere, the winter for the southern hemisphere). So what?
The “news” is connected to a theme that we have been talking about for some time: plants use the temperature and length of the day for synchronizing with the cycle of seasons And to know when the reproduction period begins. We never wondered, however, if there are special days for plants. The longest day of the year, which every June marks the beginning of summer in the northern hemisphere, for example is very important for the reproduction of the vegetation. To understand the role of the solstice for vegetation, a team from the University of British Columbia has analyzed The link between the solstice and the temperature in Europe and North America; The study is published on Pnas.
The solstice, but not only. In the northern hemisphere, what we call “Summer Solstice” falls around June 21 (it would therefore be better to call it “June solstice”, given that in the southern hemisphere it marks the beginning of winter). It is the longest day of the year, and on average, says the study, coincides with a period of optimal temperatures for the reproduction of plants.
This at least globally. At the local level, the plants also rely on other signals. In the southernmost regions of the northern hemisphere, for example, the heat comes before the solstice, and the plants must therefore take action in advance. In the northern ones, on the contrary, June could still be too cold. However important, therefore, The length of the day is not the only indicator used by plants to find out when to start reproducing.
Conflicting signals. The study also explains that there is a fundamental difference between the duration of the day and the other indicators, first of all the temperature: the first is constant year after year, while the second has larger fluctuations, which are being exacerbated, however, by global warming. According to the authors of the study, the plants are increasingly struggling to interpret these signals apparently contradictory.
The risk is to make mistakes the timing of reproduction, and find yourself a waste energy with too much advanceor on the contrary to begin the trial too late. These problems are also reflected on pollinators, who risk arriving on -site And find out that there are already no flowers, or that they have not yet sprung up. Not to mention the negative effects on crops, which also endanger us humans.
