Joshua Trees’ Early Blooms Are a Big Problem

Joshua trees are blooming months ahead of schedule this year, and scientists warn the timing mismatch could ripple through the Mojave Desert ecosystem. Typically, these iconic spiky trees, which grow across California, Nevada, Arizona, and Utah, start flowering in late February. But this season, many have already burst into bloom in October and November, according to the Smithsonian.

While early flowers might seem like a charming surprise, researchers say the shift could disrupt the trees’ critical partnership with their only pollinator: the tiny yucca moth. Without the moth, Joshua trees cannot produce fruit, seeds, or new generations of trees.

The trees and moths are engaged in an “obligate mutualism,” biologists explain. Adult yucca moths lay eggs inside Joshua tree blossoms while transferring pollen. The larvae feed on some seeds before burrowing into the soil for winter. When the trees bloom on schedule, the moths emerge, continuing the cycle. But if flowers appear months early, while temperatures remain low, the moths may remain underground, leaving blossoms unpollinated.

A similar off-season bloom was observed in 2018, mainly in the southern part of the trees’ range. This year, however, early blooms are appearing across the desert, possibly triggered by unusually heavy late-season rains, says Jeremy Yoder, a biologist at Cal State Northridge.

To help track these changes, residents of the Southwest are encouraged to photograph flowering or fruiting Joshua trees and upload their observations to the citizen science platform iNaturalist, ideally revisiting the same trees monthly, according to the Los Angeles Daily News. Researchers hope the crowdsourced data will shed light on the survival of this slow-growing species, already facing threats from habitat loss and climate-driven wildfires.

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