Cherry blossom trees bloom depends on upcoming weather, experts say

Cherry blossom trees in the Chicago area could bloom in the next few weeks if there is sustained warm weather this weekend and next week, experts say.

“Generally, if you look at the 10-day forecast and more than half the days are sunny and warm, that's a good indication that more flower emergence will occur,” said Spencer Campbell, the plant clinic manager at The Morton Arboretum.

The Chicago Park District said it wasn't ready to predict a bloom in Jackson Park, home to a grove of 190 pink-and-white cherry blossom trees. Last year, the trees didn’t hit full bloom, with officials pointing to erratic spring weather.

Sunshine is expected to return this weekend. Temperatures will rebound into the mid-40s on Friday and Saturday and upper-40s on Sunday, with a chance of showers, according to the National Weather Service. For Monday and Tuesday, temperatures are expected to reach the mid-50s to low-60s.

Usually, the peak bloom period happens in late April or early May, lasting one to two weeks.

Jacob Burns, a curator at the Chicago Botanic Garden, said with earlier springs, weather is unpredictable. If flowers open up and suddenly experience freezing temperatures, that can be “detrimental,” he said.

“Even though I'm looking at the weather forecast and I'm not seeing anything below 32 or even 28, that's not to say the weather can't change,” Burns said.

Campbell said environmental conditions, like temperature, precipitation and wind, determine the flower emergence. This spring, the Chicago area experienced warmer weather, speeding up flower development in some species by a few weeks. This was followed by recent cold weather, which “slows everything down.”

“These heavy rains and potentially snow this week will all have an impact on the cherry trees,” Campbell said.

Rapid temperature fluctuations are tough on plants. They struggle to adjust their behavior as predicted, he said.

“You bring a jacket in the morning, you're shivering. In the afternoon, you're sweating,” Campbell said. “It's hard for the plants, because they can't take off the jacket and put it back on.”

Over a 30-year trend, flowering trees are blooming sooner than historically predicted, according to Campbell.

“All that means is that we need to rethink the garden calendar. Things that we expect to emerge in mid-April may come sooner,” Campbell said.