Bloom Watch #2 | The Queens Keep Us Guessing

As hawks nest and snakes wind their way across the trails, bloom watch continues at Tohono Chul. The majority of our queens are still in their stall phase, with plump, stout buds slowly but surely putting on growth. At this point, we expect the bloom to occur sometime in the first three weeks of June, and we will continue refining our forecast as the buds develop.

The twist this season has been a round of atypically early flowering on some individuals. We had one plant bloom on the evening of Wednesday, May 13, and another on the night of Thursday, May 14.  What makes this more interesting is that, around town, our fellow bloom watchers reported early flowers on the same nights in both habitat and horticultural settings.

The mechanism behind this early flowering is unclear. Are these plants genetically predisposed to early flowering? What conditions precipitated plants around the Tucson Basin to bloom on the same night, weeks ahead of the rest of the queens? We will watch these plants to see if their gamble has paid off and if they will produce an early round of fruits full of seed for our next crop of queens.

This is why we love the queens and are always trying to learn more about them. Through our bloom records, going back to 1993 in some cases, we can follow plants throughout their lives and get to know the individual personalities of each queen in our collection. 

For instance, one of our early-blooming queens was first recorded in our collection in 2018. This plant was donated to the garden by Pima County staff who rescued it from construction work on Wilmot Road. The plant was located in a horseshoe bend on our north trail, where it benefits from the dappled shade cast by a large creosote, and the sandy soil along a shallow wash. This type of habitat is Peniocereus greggii paradise, and the plant has done well since its relocation.

In 2018, the plant had 3 flowers in June, and in 2019, it had two in July. We have no records from the COVID years, but in 2024, we recorded 3 buds, which resulted in 2 flowers in June. What the data tells us is that this plant is not known for earlier-than-average blooms. Typically, it flowers synchronously with our other queens in June or July. This suggests that something about the environmental conditions of this year prompted the early flowering of this plant and others around the region.

Now that we have passed this first exciting bloom, we are back to watching, measuring, and caring for our other plants. As always, we will keep you informed about the development of the buds and will give you as much early warning as we can about Bloom Night. Stay tuned!

– Written by Jack Dash, Tohono Chul Gardens & Facilities Manager