Why flowers bloom in spring: scientists explained

But from a scientific point of view, a logical question arises: how do plants "know" that spring has arrived? How do they determine the exact time for flowering, and with incredible accuracy from year to year?

Botanist Gregory Moore answers these questions in an article for The Conversation.

Spring is the perfect start for growth

After a cold and dark winter, the arrival of spring brings warmth, moisture and sunshine - everything plants need for vigorous growth. With competition for resources and pollinators high, plants have no time to waste: they rapidly gain strength and produce as many flowers as possible to attract insects and birds for pollination.

Flowering during this period provides an evolutionary advantage: more pollination means more chances for successful reproduction.

Pollinators are the key to success

Flowering plants (angiosperms) are relatively recent by evolutionary standards - about 100 million years ago. By this time, insects were already living on the planet and birds had begun to spread. It was these creatures that became the ideal helpers of plants in the pollination process.

Before the appearance of flowers, ancient plants reproduced by spores, and later holoderms - with the help of wind. This was inefficient. Flowering plants learnt to 'advertise' themselves - they developed brightly coloured petals, fragrance and nectar to attract specific pollinators. Spring flowering coincides with the return of migrating birds and the activation of insects after the winter pause, making it an ideal period for reproduction.

How do plants tell time?

Many people think that flowering is linked to rising temperatures. However, temperatures can be deceiving: spring cold spells or early warm days are often confusing. Instead, plants rely on a much more accurate tool: measuring the length of daylight hours.

This is helped by the pigment phytochrome, which exists in two forms and reacts to light. With this pigment, plants measure the ratio of day to night, which gives them a clear biological signal that it is time to start growing and flowering.

In addition, the hormone abscisic acid comes into play - the "brake" on flowering, which accumulates before winter. In spring, its level drops, and in combination with a long day gives green light for growth.

Why don't all bloom in spring?

Despite the obvious benefits, not all plants choose spring to flower. Some prefer autumn or even winter. This may be due to competition - the "non-standard" time allows you to attract more attention from pollinators. Or it may be due to the nature of the environment and the "orientation" towards specific insects that are active at other times of the year.