Joshua trees -- those spiky sentinels of the Mojave Desert -- are having a blossom bonanza and nobody is quite sure why.
Experts tell the Riverside Press-Enterprise that millions of trees have been bursting into bundles of greenish-white flowers in California, Arizona, Nevada and Utah.
Biologists say just about every tree has bloomed. Usually, far fewer trees blossom and they produce fewer flowers.
UC Riverside ecologist Cameron Barrows calls it a once-in-a-lifetime event.
Some have speculated that the trees benefited from late-summer thunderstorms last year or cool winter weather.
But desert biologist James Cornett believes the stress from two years of drought have pushed the plants to reproduce.
The bloom is expected to last for several weeks.
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