How do cherry trees know when it’s time to blossom?

Some cherry blossoms opened in January on Roosevelt Island, but those were juveniles, recent plantings near Cornell Tech… Youths still in search of themselves. But now, cherry blossom season is about to start with the first traditional trees budding this week. This parade will not be over until sometime in May.

Compiled by David Stone

The Roosevelt Island Daily News

Some scientists speculate that cherry trees have brains, unlike animals’, that function in ways that help and protect them. Whatever the case, something sophisticated takes place, triggering the complex internal operations that result in blossoms essential for survival of the trees.

Cherry trees don’t “know” in the same way humans do, but they do have amazing built-in mechanisms to determine the ideal time to bloom. These mechanisms rely on environmental cues, like:

Temperature:

Chilling requirement: During winter, cherry trees need a period of sustained cold temperatures (around 40-45°F) to break dormancy and initiate bloom development. This “chilling period” ensures they don’t bloom prematurely during warm spells in late winter.
Warming temperatures: As spring nears and temperatures consistently rise above the chilling requirement, it triggers the development of flower buds. Warmer days accelerate this process, while cooler days slow it down.

Daylight:

Photoperiod: The length of daylight plays a crucial role in synchronizing bloom timing. Cherry trees are sensitive to changes in daylight hours, typically blooming when days become longer (around 14-16 hours of daylight). This ensures blossoms aren’t wasted prematurely during shorter winter days.

Other factors:

Rainfall and soil moisture: Adequate soil moisture is essential for healthy flower development. However, prolonged periods of heavy rain or drought can stress the tree and delay blooming.
Genetics: Different cherry tree varieties have slightly different temperature and daylight requirements for blooming, influenced by their genetic makeup.

These environmental cues work together like a complex clock, guiding the trees through the stages of blossom development. Once they’ve met all the requirements, the beautiful floral display erupts, marking the arrival of spring.

It’s important to note that weather fluctuations can disrupt the usual blooming schedule. A particularly warm winter might bring early blooms, while a late frost can damage developing buds and delay the show.