Editor's note: If you took the Arizona Daily Star's "Measure your monsoon mastery" quiz in this past Sunday's paper, then read on. If not, then take http://azstarnet.com/news/blogs/monsoon/flash_a3130c9a-93be-11e0-b7fa-001cc4c03286.html?mode=story" target="_blank">the interactive version now!

One of the highlights of monsoon is the annual bloom night of the cereus cactus, Peniocereus greggii, better known as "Queen of the Night." Tohono Chul Park, which has the largest private collection of this cactus in the United States, keeps us all updated on when this special night will happen.

Today the park posted the following https://www.facebook.com/pages/Tohono-Chul-Park/59136301611" target="_blank">update from Russ Buhrow, its curator of plants:

"More buds have moved into a "stall" phase as they wait for the little fuzzy nubs that develop into buds to catch up. This behavior is typical and necessary since Peniocereus greggii are not self-fertile. Cereus populations, like those at our Park, bloom in synchrony, relying on pollinators like hawk moths (Sphingidae) to fly between plants and pollinate them; the larger the number of cereuses blooming simultaneously, the greater the opportunity for pollination. As in most populations though, there are always exceptions, and a couple of particularly precocious Peniocereus bloomed last Tuesday. Stay tuned!"

It's too early to predict when the cereus will bloom this year, but the park's http://www.tohonochulpark.org/wordpress/events/special-events/bloom-night/" target="_blank">website notes that buds on these cacti have formed earlier this year than in 2010. Call the Bloom Buzz hotline at 520-742-6455, extension 915, to find out the exact bloom date, or send an email to marketing@tohonochulpark.org to receive an update.

Have a weather question or a weather story idea? Send it to the Arizona Daily Star's "Thunderstruck" reporter Kori Rumore at krumore@azstarnet.com.