fallen saguaro sgp5 on Tuammoc Hill, photo by Paul Mirocha


Rest in Peace: Saguaro Genome Project #5

Saguaro SPG5, standing and fallen,
Saguaro SPG5, standing last May and fallen in August, photograph by Paul Mirocha

THERE COMES A TIME in the life of every upright being when it falls and can’t get up again. For Saguaro SGP5 on Tumamoc Hill next to the Desert Lab, it was the monsoon of last July 27.

Winds were gusting over 50 miles per hour near sunset. I was up near the summit of the Hill trying to photograph the dramatic monsoon storm coming in from the east. I gave up because the wind was blowing the camera out of my hand and almost blew me over as well. As I walked back to the road where the wind was not so deafening, I heard a loud crack. At first I thought is was the boxers practicing down below in the Desert Lab lot, but too loud for that. A gun shot? Later I realized it was the fall of SGP5.

Known for its noble bearing, poise, and generosity, lots of people knew and loved this huge old saguaro, that lived just north of the flag pole, down slope from the Desert Lab buildings. It tilted slightly off plumb line for some reason near the bottom of it’s trunk, which curved upwards as it grew to balance perfectly with gravity. That gave it an ongoing pose as it grew, like a dancer. Artists drew and painted it, especially the flowers and fruit that could be studied at eye level on its low-hanging arm, almost like it was holding out a bouquet of flowers.

It was probably about 100 years old, but no one really knows. About 30.77 feet long (9.38 meters) now that it was easy to measure.

The cactus had stood through an even stronger storm a month earlier, June 27, where winds were recorded gusting up to 70 mph. “It was getting LOTS of runoff from the flag-pole-circle road.” Saguaro roots are shallow and this one finally washed out.

Saguaro arm with flowers
SPG5 flowered in May, holding out one armful for humans to see close up.

The giant cactus attracted a group of scientists from the University of Arizona, who used tissue samples from SGP5 for the Saguaro Genome Project (Hence the initials SGP). This was the first attempt at sequencing the DNA of  a cactus. They chose a saguaro from Tumamoc Hill to honor the history of saguaro research at the Carnegie Desert Botanical Lab beginning in 1903.

After the giant cactus fell, scientists continued to take tissue samples, hoping to preserve them and get all the data they could. They even took some arms to try to root them, wondering if it was even possible to create a clone. After all, this was their type specimen. They could compare its DNA to that of other saguaros growing down into Sonora and west to other parts of the saguaro’s range.

Diagram of the chloroplast DNA of a sahuaro
Saguaro chloroplast genome map that came out of the Saguaro Genome Project. If you remember from biology class, if you were paying attention, chloroplasts have their own DNA and it’s a single large ring.

Some of the artist’s renderings of SGP5.

Saguaro Drawing in progress by Maria Johnson on Tumamoc Hill
Maria Johnson drawing Saguaro SGP5.

Maria Johnson

Saguaro SGP5 drawing by Barbara Terkanian on tumamoc hill
Saguaro SGP5 drawing by Barbara Terkanian
Saguaro SGP5by Meredith Milstead
Saguaro SGP5by Meredith Milstead


3 thoughts on “R.I.P. SGP5

  1. Paul,
    Thank you, a very nice tribute to a fallen giant.

    Marty Wojciechowski, Professor at Arizona State University, and one of the “co-conspirators” that initiated the Saguaro Genome Project.

    You may remember me – I was in the EEB department at the university in the late 1980s to 1997. You designed the “tree of life” image that became the centerpiece symbol for the NSF sponsored Research Training Group in The Analysis of Biological Diversification (we used it on our flyers and t-shirts); I was program coordinator for the program

Leave a Reply

Your email address will not be published. Required fields are marked *