Southern California’s iconic Joshua trees started flowering months ahead of schedule this year, raising alarm bells for scientists — who are scrambling to help crack the mystery.
Typically, the Mojave-dwelling succulents start flowering in February and April, drawing the yucca moth to pollinate the flowers so they produce fruit, which drops to the ground and gets gobbled up by rodents. The plant’s seeds then get spread in the course of the animals’ travels.
This year, however, for unknown reasons, the familiar white-and-yellow flowers started appearing on Joshua trees in late October, raising questions among scientists about the trees’ fruit production this year and the downstream effects on the species’ propagation.
The troubling sign comes at a time when the famous trees are already struggling in the face of wildfires and extreme weather conditions.
California State University, Northridge associate biology professor Jeremy Yoder told SF Gate the early blooming could threaten the yucca moth — Joshua trees’ only pollinator — whose evolution has synced with the predictably timely blossoming of their flowers.
Yoder told the outlet the moths’ lifecycle is directly linked to the Joshua trees’ blooms. They deposit pollen, and their larvae grow within the fruits, eating some of the seeds before they “chew their way out of the mature fruit, drop to the ground, and burrow into the sand and form a cocoon” until the next cycle begins.
“The moths are totally dependent on the trees. The trees have no other pollinators because the moths are so good at their job,” Yoder said. “And so the real question when the trees flower super early like this is: Are the moths going to show up? And what I think we’re seeing so far is that they’re not.”
He said he suspects this year’s early rains played a part in the premature flowering. His Yoder Lab is soliciting members of the public to help document the phenomenon by uploading photos of Joshua trees in bloom to iNaturalist in an effort to help scientists gather more data to determine whether it will impact their ability to bear fruit.
“We’re looking for as many folks out there as possible to help observe this phenomenon,” Yoder told the outlet.
A similar early bloom happened in 2018, though it predominantly only affected trees in Joshua Tree National Park, the furthest south where they are known to grow. This year, Yoder said, the early flowering is happening everywhere the trees inhabit.
The hope for the data collection is that photos taken by the public in 2018 observed alongside photos taken this year will help scientists better assess the impacts of early blooms.
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“If the trees are flowering more frequently, but the moths don’t show up to match that, then the trees are spending energy and effort, and that might make them less resilient to stress, and that spent effort doesn’t result in new seeds and new Joshua trees to replenish the population,” Yoder told the outlet.
“But that’s the possibility. That’s what we don’t know.”
