Editor's note: This story was originally published in May 2023. We've updated the story with relevant information for the 2024 saguaro bloom season!
Saguaro blooms are back. 😎
Saguaro bloom season is happening across Tucson and Southern Arizona right now and that means you can find many cacti topped with soft white blooms.
While some saguaros are already showing off their flower crowns, this year’s blooming season is a little late compared to other seasons, according to Erin Posthumus, the partnerships and projects manager at USA National Phenology Network and a researcher at the University of Arizona.
“The main thing that I've noticed this year is it's kind of late compared to our record of the last 10 years,” she said. “And I've seen other people commenting on it as well. It seems like they were a little slow to start, but they're blooming now and we're seeing both flower buds and open flowers.”
Typically, you’ll start to see flower buds around mid to late April followed by open, blooming flowers around May.
“We're looking at a couple of weeks later than that. So, we were just starting to see open flowers the first week of May and that, for our records, is pretty late,” Posthumus said.
However, Posthumus estimates that many saguaros should bloom by Mother’s Day.
Because cacti store water extremely well, they don’t rely on rainfall as much as other plants do for a prosperous blooming season.
But rainfall and heat can impact when we start to see blooms in Tucson.
“It seems like in years where we have more winter rains, you'll see a delayed onset and so I think that's probably what's going on here,” she said. “We had a really nice winter monsoon with lots of rain and so I think that's part of it. Another thing I noticed from looking at the news and the temperature data is that we're actually kind of behind schedule in terms of the amount of heat that we've accumulated this year. So, that could be another contributing factor. It just hasn't been very warm this year yet.”
When saguaro blooms finally make their arrival, they aren’t here for long. Their lifespan typically lasts one day — so it’s best to enjoy them (and their melon scents) while you can!
“The flowers will typically bloom at dusk or later and exist until the following day when they wither away. During a saguaro's bloom, the flower could be pollinated by many Sonoran Desert creatures including bats, doves and bees,” #ThisIsTucson wrote in 2022.
A saguaro bloom located at Saguaro National Park East near the Cactus Forest Loop Drive.
Saguaros are a “keystone species” in our ecosystem, according to Theresa Crimmins, the director of the USA National Phenology Network, who says that many desert creatures rely on the tall cacti for homes and food.
“Once a saguaro flower has been pollinated, it matures into fruit that splits open when ripened — revealing bright red pulp,” #ThisIsTucson wrote in 2020. According to the Arizona-Sonora Desert Museum, each piece of fruit contains about 2,000 small black seeds.
Saguaros also produce blooms in a pattern, so don’t expect to find all saguaros blooming at the same time, according to Posthumus. Locals can report their findings to the USA National Phenology Network’s Nature’s Notebook campaign to help keep track of how many blooms saguaros are producing this season.
This season, you can find blooms in the Tucson Mountains, especially as you’re heading west toward Gates Pass, along the bottom of Mount Lemmon Highway and around Saguaro National Park East, Posthumus says. (You may or may not catch #ThisIsTucson's editor, Gloria Knott, standing on a step ladder next to a saguaro to get that perfect shot of the blooms at Saguaro National Park.)
“The blooms are so important for saguaros and being able to form the next generation of saguaros,” she said. “And we have seen a lower amount of new saguaros growing each year so we're hoping that there's a good bloom and we hope that those blooms get fertilized by pollinators.”
