Experts says more rain and mild conditions this winter could mean the difference between a good wildflower bloom like one on the left at Picacho Peak State Park in 2020 or a bad one like the one on the right in 2021.

 Henry Brean, Arizona Daily Star

Winter has only just begun, but wildflower forecasters are already looking forward to spring.

So what might the recent rains in the desert mean for next year’s bloom?

“Every botanist out there is pondering the same question,” said Jim Malusa, research scientist with the University of Arizona School of Natural Resources and the Environment. “Nothing motivates the seeds of spring annuals better than an early winter rain, but how much rain is enough rain?”

So far this month, the National Weather Service has recorded 1.19 inches at its official gauge at Tucson International Airport. That’s a little over twice the normal amount for this time in December, thanks to a pair of weather systems about nine days apart.

Malusa said both storms were pretty widespread from Nogales to Casa Grande and delivered enough moisture to spur growth in at least some of the seeds still hiding in the ground from previous blooms.

Desert ecologist Ben Wilder said the rain so far has been a nice surprise considering we’re supposed to be headed into our second straight La Niña winter, which typically means dry conditions in the Sonoran Desert.

“The timing has been pretty ideal to really bump up the soil moisture and have that sustained for about a month,” Wilder said.

He thinks more rain needs to fall to spark a widespread bloom, but areas such as Picacho Peak did well enough during the first two storms to trigger germination.

“Now the concern is freezes,” Wilder said.

The first cold snap shortly after the recent storms probably didn’t pose much of a threat to the newly sprouting seeds, he said, but subsequent ones will.

“I would say chances are good for some decent flowers around the Picacho Peak area if additional freezes hold off,” Wilder said. “And they could be good or really good in that area — and more regionally — with additional rains in the coming weeks.”

Mark Dimmitt is the retired director of natural history at the Arizona-Sonora Desert Museum. Now he maintains a sprawling collection of unusual plants in his garden and greenhouses on Tucson’s west side.

A few varieties of wildflowers popped up at Wilson Avenue and Juanita Street in the Catalina Vista neighborhood in 2020.

He said the ground in his neighborhood is already “greening up” from the rain so far this month on the eastern slope of the Tucson Mountains, hinting at a “mass germination of annual seeds.”

Unfortunately, the desert may have already missed its chance for anything better than a decent show of color.

“The ideal formula for a massive wildflower bloom is a soaking rain in October or November, followed by at least an inch of rain per month through February,” Dimmitt said. “This December start is a little late, but the bloom could still be good if the winter is on the warm side so the seedlings can make good growth before warmer spring weather stimulates flowering.”

An “anomalously wet winter rainy season” would also help, he said, though La Niña may have other plans.

If you can’t wait until spring to see some flowers, Dimmitt said he’s getting early reports — and a few photos — of “sand verbena, desert sunflower and a few desert lilies” that are already in bloom at Anza-Borrego State Park in California‘s Mojave Desert.

Closer to home, though, Malusa said it is still too soon to know anything with certainty — even with the promising storms earlier this month.

“Last year we also had 1 to 2 inches around Tucson in December, and then less than an inch until the summer monsoons arrived. The spring annual bloom was a dud,” he said.

But Malusa is more of a field-is-half-full kind of guy when it comes to wildflowers. Even during a down year, the desert can still surprise you, he said.

“If the rains fail in January and February, there are always brittlebush and baby bonnets and palo verde — perennial shrubs and trees that, with meager spring rainfall, still most always provide a spring show,” Malusa said. “The palo verdes were fabulous last year.”

Cactus blooms are more reliable than wildflowers because they require less rain. With enough water, they can have multiple bloom cycles. Photos by Doug Kreutz, Arizona Daily Star

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Contact reporter Henry Brean at hbrean@tucson.com or 573-4283. On Twitter: @RefriedBrean