Bloom Watch #3 | A Royal Growth Spurt

Monsoon Magic

Last Friday morning as Chris Kibler, Senior Gardener here at Tohono Chul, made his rounds on the Desert View Trail, he noticed that the buds on the Queens were still small and tightly closed; but a lot can change in a few days. Bloom Night is approaching much faster than we originally predicted!

The summer solstice began blanketed in a dusty haze. A nebulous veil covered the mountains and a strong wind swept the city. Sand was carried over hundreds of miles high in the sky across the Southwest from New Mexico; a cloud of seeds.

By Friday afternoon, the weather was shifting. The dry heat, a trademark of June in Tucson, began to moisten. Clouds were forming to the east which soon spread over the horizon. “We’re crossing our fingers that we get some rain,” said Chris. That very next afternoon, the familiar, earthy smell of petrichor filled the air. Puffy cumulonimbus clouds formed over the Catalinas. The sky opened up and delivered the first Monsoon of the season, quenching the desert’s thirst and feeding the Queens.

I’m sure you have noticed the increased humidity this week. Doors are swelling. You can cut the air with a knife. This consistent humidity has done wonders for plant life throughout the garden and surrounding desert. It’s almost as if you can see things growing in real time.

The Queens have experienced rapid growth since Saturday’s storm, doubling in size over the course of the week.
Buds are turning color with bits of deep maroon peeking through, hinting at the petals growing just beneath.

Due to this rapid growth spurt, we anticipate Bloom Night to occur sooner than expected. That’s right — the Queen is coming! We predict that the buds will grace us with a royal show either late this week or early next week. Last year, they chose July 23rd as their day. Which day will our resident monarchs choose this year? Will it be this weekend? Maybe. All we can do in the meantime is measure, observe, and wait.


The Queen’s Court

Meanwhile, at the Overlook, Chris discovered that our Peniocereus collection, known as the Queen’s Court, has sprouted 79 buds!

The Queen’s Court (located at the Overlook on the southern side of the gardens) displays our diverse Peniocereus collection.

The Queen’s Court collection is a great example of the remarkable diversity found within the Peniocereus genus. These unique plants are native to the Southwest US and Mexico, flourishing in varied and distinctive habitats; from the creosote flats and gravelly slopes of the Sonoran and Chihuahuan deserts to the dry tropical forests of Western and Southern Mexico. For example, Peniocereus serpentinus can be commonly found growing in the understory of mesquite woodlands. At the same time, the Peniocereus marianus has been spotted sprouting from a sheer basalt cliff on the Sinaloan coast.

Details of buds from the Queen’s Court (left to right): Peniocereus cuixmalensis, Peniocereus oaxacensis, Peniocereus maculatus

Buds in the Queen’s Court have begun to bloom sporadically, much to the delight of local pollinators. Bats, birds, and insects, especially certain moths, eagerly await their late-night snack. Since the Queen of the Night blooms only once a year, pollination is critical to its survival.

Pollination is the reproductive process of plants where pollen is transferred from one flower to another, enabling seed and fruit production and ensuring the next generation of plants. The Peniocereus greggii relies primarily on nocturnal pollinators, particularly sphinx moths (Sphingidae), for this essential process.

The white-lined sphinx moth is an important pollinator for the Peniocereus.

The Queen of the Night’s flowering behavior, scent, and structure are finely tuned to attract nocturnal pollinators. Its large, bright, tubular flowers are typical of plants pollinated by moths. The narrow shape facilitates easy access, allowing them to hover and reach deep into the flower with their proboscis, a straw-like mouthpart used for feeding.

Soon, the desert will be alive with the fluttering of moths and the sweet scent of blooming Queens.


Bloom Watch is written by Tracey Till, Propagation Coordinator


The Queen is Coming…

Due to rapid growth from recent rain and increased humidity, we predict Bloom Night to occur sometime within the next 7 days, potentially as soon as this weekend.

Sign up for Bloom Watch emails here.
Be sure to select “Bloom Watch” on the dropdown menu.


Members Only

This year, Bloom Night is an exclusive members-only event. Your support helps preserve the Desert View Trail and our Peniocereus greggii collection while we work to ensure proper pollination of these special plants.

Don’t miss out—become a member today and unlock a year of perks and benefits at Tohono Chul, including early access to plant sales, discounts, free daily admission, reciprocal admissions at other public gardens, and much more.


Predictions and estimates for Bloom Night are subject to change based on various factors such as weather conditions, growth patterns, and environmental influences.

Bloom Watch #2 | Beneath the Surface

Tohono Chul Gardeners Chris Kibler and Shauna Smith, along with dedicated volunteer Tammy, have been diligently watching over the Queens and measuring their progress.

Shauna and Chris recorded measurements of the growth of the buds for our records. “Most are at 40 mm, with a few near 60mm. With the onset of this heat they’ve slowed down.” said Chris, Senior Gardener at Tohono Chul. According to the Gardeners, Bloom Night could be anywhere between 2-4 weeks out. But as we all know, Mother Nature works on her own timeline.

Stems grow from the tips. Concentrated spines and fuzz help protect the area where cell division is occurring on a Peniocereus greggii, the night-blooming cereus.

I ventured out to the Desert View Trail early Tuesday morning to see the Queens for myself and hear what the trail has to say…

Larrea sparkle in the morning sun, as if covered in dew. Seeds waiting for the winds of change, the monsoon.
A gossamer seed released like a puff of smoke, floats by.
Spiderwebs glisten between branches, the invisible is visible.
Every tree is a tree house for the beetles and bees. You can see the small oval holes like windows.

A wasp, brown and red, hovers over a Queen of the Night.
Flowerbuds! They decorate the plant like little black and white flames. Star-shaped spines cling to the trunk of their nursery tree, an acacia.
Amongst the wild trees and grass the soil is covered in white and orange stones.
Gneiss stones freckled with garnets slowly worn away into sand by streams of rainwater and wind.

Many small footprints appear in the dusty, well-worn path. Hoof, paw, and claw. An occasional sneaker print from a Tucsonan.


My walk makes me wonder, what is this gravelly soil made of anyway? Why does the Peniocereus greggii grow here and not everywhere?

Heading back to civilization and leaving the peaceful morning vista, I’m sitting at my desk. I decided to let my curiosity stray from the winding paths of the Desert View Trail and onto the winding paths of a Google search. I came upon the Web Soil Survey website (provided by the USDA) and looked up the Desert View Trail’s location on their interactive soil map. Now, soil science is a foreign language to me, so I must read slowly to understand… “Alluvium derived from schist and/or alluvium derived from gneiss… along with other granitic and some volcanic and sedimentary rock”.

Screenshot from the Web Soil Survey website.

Okay, let’s break this down!

Alluvium is made of sand, gravel, silt, and clay deposited by flowing water. According to their website, The Desert View Trail and much of the surrounding area were likely formed during the Ice Age when mountain glaciers melted and produced lakes and rivers that deposited these sediments. Over time, calcium carbonate was also formed as slightly acidic rainwater trickled through the layers. The expanse of time; the natural forces of water, wind, and sun that shaped the landscape is awe-inspiring!

It seems the Queen of the Night is well adapted to the sandy, silty, gravelly soil. Perhaps adequate moisture and drainage are all that is necessary to allow the large tuberous root to grow and to prevent rotting.

Earlier, botanist and Tohono Chul Gardens Manager, Jack Dash, brought up the question to me of whether the baby Queens we are growing in the nursery could benefit from symbiotic microbes native to the desert soil.

Perhaps more is going on than can be easily seen. What else could be going on beneath the surface? Soil is not only a collection of tiny non-living rocks but a thriving and bustling community and ecosystem. It’s filled with active plant roots, algae, fungus, bacteria, and small invertebrates.

This graphic depicts the intricate web of microbial interactions within a soil ecosystem. Vibrant colors and organic shapes represent the diverse array of bacteria fungi and other microorganisms.

Many people know about the miraculous mycorrhizal (fungi that have a symbiotic relationship with the roots of many plants) that colonize tree roots and enable them to absorb more nutrients from the soil. It turns out that cactus also facilitate partnerships with fungi friends! According to the book Cactus Biology and Uses, root samples of different Sonoran cactus species were anywhere from 10% to 70% colonized by mycorrhizal fungi.

However, I have yet to dig up an article specific to Peniocereus greggii mycorrhizae. What might be happening beneath the soil of our Queens? For now, it remains a mystery to me.

The Queen knows where to grow. The Queen knows when to bloom. When she is ready.


Bloom Watch is written by Tracey Till, Propagation Coordinator


We are estimating about 2 to 4 weeks away from the big night! 
Stay tuned for updates.

Click here to sign up for Bloom Watch emails.
Be sure to select “Bloom Watch” on the dropdown menu.


Members Only

This year, Bloom Night is an exclusive members-only event. Your support helps preserve the Desert View Trail and our Peniocereus greggii collection while we work to ensure proper pollination of these special plants.

Don’t miss out—become a member today and unlock a year of perks and benefits at Tohono Chul, including early access to plant sales, discounts, free daily admission, reciprocal admissions at other public gardens, and much more.


Predictions and estimates for Bloom Night are subject to change based on various factors such as weather conditions, growth patterns, and environmental influences.

Bloom Watch #7

Another rogue player …

“It looks like we have another rogue cactus on our hands!” said Chris on Monday morning. 

Queen of the Night #379 is at the head of the pack with two buds measuring 110mm and on track to bloom this week. The rest of the regal monarchs are still between 40mm-60mm. 

“With the increase in humidity this week, (40% this morning!) they may pick up the pace. I’ll definitely keep you all posted.” he says. 

“The Queen’s Court at the Overlook has several cacti ready to bloom. One was blooming Friday night! Check them out if you’re brave enough to go outside!” 

Gardens Manager, Chris Kibler, shows where one of the lighting units is installed above a bloom location in eager anticipation of Bloom Night.

A Botany Lesson

Speaking of the Queen’s Court (the row of potted cacti positioned at The Overlook here at Tohono Chul), one of the courtiers, Peniocereus striatus, illustrates a fascinating example of convergent evolution in the plant kingdom. Convergent evolution is the process of distantly related organisms evolving similar traits in order to adapt to similar situations. Introducing, Euphorbia cryptospinosa, native to the landscapes of Ethiopia, Somalia, and Kenya.

Euphorbia cryptospinosa close-up of stems. (Photo courtesy of Dave’s Garden davesgarden.com)
Euphorbia cryptospinosa: Flowering plant in cultivation. (Derivative of a photo by Frank Vincentz, contributor to the collection of photos courtesy WorldofSucculents.com)

This completely unrelated plant from the opposite side of the planet has been shaped by it’s own climate to look much like our Peniocereus striatus. Both have tuberous roots, with slender cylindrical stems that are camoflagued amongst the shrubs where they both grow in sandy, gravely soil. In addition to being succulent, both have developed an ingenious way of preventing extra water loss during drought.

Stomata are unique to plants and are the specialized groups of cells that open and close to allow for gas exchange of CO2, oxygen, and water vapor, through the epidermis of a plant. In our courtier and our friend the Euphorbia cryptospinosa, the stomata are restricted to narrow furrows that run vertically along the stems. When they have acquired sufficient moisture, these stems are plump and the stomata are more exposed to the air to enable gas exchange, but still shielded from the wind.

When the plant stems lose water, the furrows are sucked in from this water loss and they begin to close up like an accordion. By enclosing their stomata this way, they preserve their thin stems from shriveling up, even in very dry habitats. By studying comparative anatomy in this way, we can learn a lot about how plants work. Thanks to the University of Arizona Herbarium for providing this research for free so we can all level up our botany!

(Source: https://cals.arizona.edu/herbarium/sites/cals.arizona.edu.herbarium/files/old_site/assoc/people/rfelger/1997_felger_henrickson_convergent_evol.pdf )

By Tracey Till, Propagation Associate

Don’t miss the big night! Sign up for Bloom Watch emails here. 
Be sure you select “Bloom Watch” on the dropdown menu!

Bloom Watch #5

Cruel Summer

This is when we remember why it’s called the desert. The insects in the trees seem to imitate the sizzling Sonoran heat. Critters take refuge in the shade and their cool burrows. They drink from the fountains and hoses as we water the flowers. Days are long and the sunsets beautiful. Saguaro seeds disperse in the full bellies of birds. Prickly pear fruit turns color. 

Waiting for rain.

One of our dedicated gardeners, Shauna, performed her weekly duties of tending to the Queens by providing them with the necessary watering. Supplemental water ensures the vitality of these special plants during times of excessive heat and lack of rainfall.

“I’ve been watching, and the rain in the forecast keeps getting moved a day farther away,” she said. The buds we checked this week were between 40mm and 50mm.  

“No real change from last week.”  We are still approximately 1-2 weeks away from Bloom Night.


Cooking Up A Storm 

The University of Arizona’s CLIMAS has this to say about our monsoon season: 

“The monsoon is driven by the sun heating up the land and the Pacific Ocean at different rates, with land surfaces warming more quickly than the ocean. The warm land creates low-pressure zones as hot air rises… The moisture-laden monsoon air travels north to Arizona and New Mexico, encouraged by the pressure difference between the hot, parched southwestern air and the cooler Mexican air.” (source)

We might never know exactly why the Queen decides to bloom when she does, but from careful observations collected over the years in our little patch of desert, it seems to be closely linked with the occurrence of this pattern. 

Tohoho Chul’s water harvesting garden, Sin Agua, in 2022

It’s a busy time and a slow time here in the desert. A hurry up and wait. Where there is water, there is abundant growth. In our nurseries and in the garden we are all trying to keep up with the vigor of our plants as they soak up this solar energy. But by mid-afternoon, there is a quiet in the garden. The desert has some time to herself. 


Rebel Flower Update

If you’ve been keeping up with Bloom Watch, then you know that last week we had a rebel flower on our hands. One of the Peniocereus greggii buds decided to bloom ahead of schedule, catching our gardening staff by surprise.

As always, the unpredictable nature of these special plants is keeping us on our toes. But fear not, nature enthusiasts! The rest of the buds are on track and expected to grace us with their beauty in approximately 1-2 weeks.

Stay tuned for more updates as we inch near the arrival of the Queen (the rest of them, that is)!

By Tracey Till, Propagation Associate

Don’t miss the big night! Sign up for Bloom Watch emails here. 
Be sure you select “Bloom Watch” on the dropdown menu!

Bloom Watch #1

The Queen is Coming

Chris Kibler, Gardens Manager at Tohono Chul, is watching the Queen of the Night cacti and measuring the flower buds at least twice a week now. Most of them are showing new growth thanks to the plentiful winter rains we received. As of today, Chris has found fifteen Peniocereus greggii flower buds; some others are too small to tell. Four of the buds are located right outside the Children’s Garden near the Desert View Trail.

The fuzzy white branch tips and buds are the telltale signs of new growth beginning. The Queen is waking up.

Aside from these night-blooming cereus buds, The North Loop is brimming with a vibrant spectrum of cactus blossoms. We highly advise taking a leisurely stroll while you await the arrival of The Queen!

Rain, surprise. 
Snowy fruit. 
Bathing in the scent. 
Beetles hide in prickly pear blossoms,  
Goldfinch gather chia seeds. 
Quails hurry, lizards lounge. 
The Queen stretches; her white hair begins to grow.

By Tracey Till, Propagation Associate

We are estimating about 4 to 6 weeks away from the big night! 
Stay tuned for weekly updates.

Sign up for Bloom Watch emails here. Be sure you select “Bloom Watch” on the dropdown menu!