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.
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 yearโs bloom?
โEvery botanist out there is pondering the same question,โ said Jim Malusa, research scientist with the University of Arizona School of Natural Resources and the Environment. โNothing motivates the seeds of spring annuals better than an early winter rain, but how much rain is enough rain?โ
So far this month, the National Weather Service has recorded 1.19 inches at its official gauge at Tucson International Airport. Thatโs 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 weโre supposed to be headed into our second straight La Niรฑa winter, which typically means dry conditions in the Sonoran Desert.
โThe timing has been pretty ideal to really bump up the soil moisture and have that sustained for about a month,โ 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.
โNow the concern is freezes,โ Wilder said.
The first cold snap shortly after the recent storms probably didnโt pose much of a threat to the newly sprouting seeds, he said, but subsequent ones will.
โI would say chances are good for some decent flowers around the Picacho Peak area if additional freezes hold off,โ Wilder said. โAnd they could be good or really good in that area โ and more regionally โ with additional rains in the coming weeks.โ
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 Tucsonโs west side.
He said the ground in his neighborhood is already โgreening upโ from the rain so far this month on the eastern slope of the Tucson Mountains, hinting at a โmass germination of annual seeds.โ
Unfortunately, the desert may have already missed its chance for anything better than a decent show of color.
โThe 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,โ Dimmitt said. โThis 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.โ
An โanomalously wet winter rainy seasonโ would also help, he said, though La Niรฑa may have other plans.
If you canโt wait until spring to see some flowers, Dimmitt said heโs getting early reports โ and a few photos โ of โsand verbena, desert sunflower and a few desert liliesโ that are already in bloom at Anza-Borrego State Park in Californiaโs Mojave Desert.
Closer to home, though, Malusa said it is still too soon to know anything with certainty โ even with the promising storms earlier this month.
โLast 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,โ 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.
โIf the rains fail in January and February, there are always brittlebush and baby bonnets and palo verde โ perennial shrubs and trees that, with meager spring rainfall, still most always provide a spring show,โ Malusa said. โThe palo verdes were fabulous last year.โ