MORONGO BASIN — How do you trick a Joshua tree? Apparently, it takes 2 inches of rain and temperatures dropping as much as 10 degrees below normal.
Desert ecologist James W. Cornett thinks that might be why a handful of Joshua trees and Mojave yuccas are throwing out blooms around the Morongo Basin this month — when it is definitely not their flowering season.
“I never dreamed that I would see something like this happen,” Cornett said in a phone interview this week.
“As far as I’m aware, this has never happened before, and I’ve been studying Joshua trees intently in the Joshua Tree National Park area since 1988.”
Cornett’s theory is that the trees and plants are reacting to October’s unusually high rainfall and low temperatures.
“This October was a fluke. We got more rain than normal and temperatures were cooler,” he said.
Thanks to an Oct. 13 rainstorm that unleashed as much as 2 inches of rain in parts of the desert, rainfall in October 2018 was 4.4 times above the Basin’s long-term average.
The daily maximum temperature throughout the month was 4 degrees below normal and the minimum overnight temperature was 10 degrees below normal, according to Cornett’s research.
Usually, Joshua trees and yuccas bloom as early as the last week in January — the month that’s typically the coolest and wettest of the year.
“My hypothetical explanation is this October was kind of like January. It was cooler than normal and you got quite a bit of rain,” he said.
It’s possible, he thinks, that those blooming Joshua trees and yuccas reacted as though January is already here.
Cornett spent two days in the field cataloging the unexpected blooms, examining more than 400 Joshua trees and finding nine with flowers. He estimates around 2 percent of Joshua trees are blooming right now, and possibly 3 percent of yuccas.
“What happened was that most of the Joshua trees weren’t fooled by this sudden onslaught of rainfall or cool temperatures, but some were.”
He also noticed that while Joshua trees in spring usually explode with several flower clusters, the ones blooming now are putting out at most one or two. He is guessing that these trees and plants didn’t bloom last spring, leaving them with a smidgen of the hormone that triggers flowering.
“Those trees and plants have a little bit more of the blooming hormone, residual from the year before, and that was enough to trigger a little bit of flowering,” he theorized.
“They thought it was January, if you will, and they put out one or two inflorescences. We call the whole flower cluster inflorescences.”
He doesn’t think this is a new mutation in the vegetation’s makeup: “I don’t think this is an anomaly; I think the trigger has always been there, it just never happened before.”
Can the yucca moths be tricked, too?
If the Joshua trees were fooled, will the same fate befall their pollinators, the yucca moths?
During the fall and winter, the moth larvae lie buried in cocoons beneath the surface, waiting for the spring.
“The moths are in the ground and they’re waiting for the right signal,” Cornett said. Scientists aren’t positive exactly what that signal is, but it’s likely it’s the rainfall and low temperatures of January.
It will be obvious if the moths do make their way above ground and start feeding on the flowers’ pollen: If they’re pollinated, the flowers will turn into the big green fruits desert residents are used to seeing in the late spring and summer.
The good news: They can change
While it may have been a fluke, Cornett thinks the freak bloom might be a good sign for the future of the Joshua tree — a plant threatened by climate change, according to several scientific surveys.
He’s cautions about drawing conclusions, but it’s possible Joshua trees might be a little more adaptable than previously thought.
“Whenever we see behavioral or physiological adaptation, that’s a good sign, because it suggests these plants may have an ability to adapt to a new climatic regime,” he said. “There may be advantages to being able to bloom in the fall.”
It’s also possible that a changing climate is responsible for the bloom. While October was unusually cool and wet, over time, the climate in the Mojave Desert has gotten warmer and drier; nighttime lows have risen nearly 8 degrees above average in the past 40 years in Twentynine Palms, according to ecologist Cameron Barrows.
“Is this a coincidence that we now can definitely say we are looking at a change of climate and suddenly the Joshua trees start blooming in the fall? I can’t answer that yet,” Cornett said.
“We start looking for anomalies now. Things that weren’t happening are starting to happen. Is it the result of that big rainfall or is it a shifting climate?” He just isn’t sure.
“In any case, plants that are able to shift how they do things are more likely to survive.”
What’s certain is it’s an exciting time to be a research ecologist, watching adaptation play out before your eyes.
“This is a scientists’ once-in-a-lifetime chance,” Cornett said. “This made my year.”