As spring weather settles over the Northern Hemisphere, those barren branches will soon be bursting with color. Just like humans, plants have a circadian clock which helps them tell time. They rely on seasonal changes to both air temperature and sunlight to know that winter is on its way out and that it’s time to bloom. Plants can also tell when we’re stressed out.
Longer days and warmer temperatures are the seasonal cues for plants that bloom in the spring. Plants with leaves are particularly sensitive to sunlight, which steadily increases from March until the summer solstice in late June. For plants like daffodils and tulips where the flower comes out of the ground or on branches like cherry trees, increasing temperatures are their main cue to bloom.Â
University of Washington chronobiologist Takato Imaizumi shares more about how our planet’s plants sense these seasonal changes.
How do plants know when to bloom? Spring flowering explained by UW chronobiologist
California’s notorious hot and dry Death Valley saw a wildflower superbloom this year thanks to extra rain. While the bloom is past peak in some locations, higher elevations will see blooms from April through June. You can follow along with the bloom’s progress via Death Valley National Park’s website.Â
Washington DC’s famed cherry blossom trees are also projected to reach peak bloom March 29 through April 1. The yoshino trees that dot the National Mall typically bloom for several days. The length depends on weather conditions. Cool and calm weather can extend the length of the bloom, while a rainy, windy day can halt these delicate blossoms. A late frost can also prevent the trees from blooming at all. You can follow their progress on the NPS’ Cherry Blossom Festival website.Â
In Ask Us Anything, Popular Science answers your most outlandish, mind-burning questions, from the everyday things you’ve always wondered to the bizarre things you never thought to ask. Have something you’ve always wanted to know? Ask us.
Â
2025 PopSci Best of What’s New
Â
