Monthly Archives: July 2013

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Cholla

Cholla and prickly pear cacti are closely related inhabitants of the Sonoran Desert, although there is scientific discussion about exactly how closely related they are. Both are segmented cacti that form new joints with each growing season instead of just extending their existing forms as barrel cacti and saguaros do. Both reproduce through vegetative means, by rooting segments that fall to the ground around them. Some cholla reproduce exclusively this way; although their fruits do produce seeds, as do those of prickly pear cacti, their seeds rarely or never germinate, and new plants merely spring up from the segments that have fallen to their feet. It’s possible to find large stands of cholla that are all clones from one original plant.

Arizonans have a love-hate relationship with cholla. On the one hand, they’re natives that are worthy of respect because they survive in landscapes that are too dry even for prickly pear. On the other hand, anyone who unwarily steps too close to a jumping cholla will discover very quickly how the myths arose that gave them their common name. Joints between the segments are so fragile that even the slightest brush against one of them will detach it, and its barbed spines will lodge themselves firmly into fabric or flesh for transportation to a new place to take root.

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Spiny Lizard

DSCN0151As I left my office last night, I caught sight of this lizard on the sidewalk outside. According to A Natural History of the Sonoran Desert, the orange head indicates that this is a female in the breeding season. She watched as the people around me left for the day and stayed in place while I fumbled my camera from my purse, waited while I shot a few frames and then skittered away into a drain below the sidewalk.

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Saguaro National Park

This morning I visited the Rincon Mountain Unit of Saguaro National Park. I’d driven past its entrance a few times in the past few years, and I can’t say that it made any sense at all to pick July as the time for a first visit. I checked in at the ranger station at around 8 a.m., behind a flock of bicyclists, with a ranger who asked me if I had plenty of water along and then assured me that if I kept my eyes open, I’d probably see some animals.

I was only a few hundred yards inside the park when my attention was captured by a female cardinal that flew across the Cactus Loop Road in front of me and perched on a tree by the roadside for only long enough to turn her head so I could see her crest silhouetted against the sun. Before I could stop the car and take my camera from its case, she’d disappeared into the brush. A few minutes later, I saw the bright scarlet flash of a male high in a tree on the other side of the road.

And thus it was throughout my visit — I caught sight of several birds and heard the calls of many more. I saw several rabbits as they raced across the hiking trail in front of me, and I saw lizards as they skittered from beneath one shrub to the next. Not one of them did me the honor of posing for a photo.

This is one of the many reasons I love to photograph wildflowers and trees — they’re so much less determined to escape from my lens. Every plant I shot today simply remained in place and patiently allowed me to shoot from as many angles as I liked.

I hadn’t expected to see any flowers today. Most of our desert plants flowered and set seed months ago, giving the seeds time to germinate and the plants to get a little jump on the summer’s heat, so it was a surprise to see yellow flowers blooming away just at the edge of the road. After my drive through the park, I stopped in at the visitor center and asked a young ranger what those yellow flowers are that are blooming right now. “We have a lot of yellow flowers,” she said as she reached for a binder. “Maybe we can find them in here.”

“I have pictures,” I said and showed her the camera.

DSC04903“If you have pictures, that’s really going to help,” she said. I scrolled through the photos until I got back to a shot of the plant that showed leaves as well as flowers. She looked dubiously at it. “I don’t think we’re going to find that one in here,” she said, and she closed the notebook.

Another ranger came up and leaned over me to look at my camera screen. “That’s desert senna,” he said casually and then continued on his way.

The ranger with the notebook brightened and went across the room to the display of books for sale, pulled out a guidebook and brought it over for me to look at the entry for Desert senna. And there it was.

Desert senna, Senna covesii, is a legume, related to the pea, It’s a short shrubby perennial that can be as much as two feet high. Flowers are bright yellow with five separate and prominently veined petals that form a corolla around orange anthers. The plant has a long flowering season, particularly when there is abundant moisture from summer rains.

Well, that explains why it was blooming all over the place today. Our summer monsoon season has started, and southeastern Tucson got an inch of rain about a week ago. Desert plants don’t waste time after a shower like that — they’ll bloom in astonishing profusion when Nature has given the signal that the soil may hold enough moisture to allow seeds for the next generation to germinate. 

After I’d photographed the flowers, I drove a little further up the road and stopped at a trailhead for a short hike, still hoping that I’d see animals that would hold still and pose for me. No luck, so I settled for saguaros, which always amaze me for the lessons they teach about making the best of the environment in which you find yourself. Saguaros grow under the shade of nursery plants on well-drained slopes, so quite often you’ll see them nestled in next to a tree or another cactus that they may have outgrown over time.

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The odds against their survival are high while they’re young, but once they get past their first youth, they can live a long time. Cactus wrens take up residence in holes drilled into them, and they seal off the nest holes and grow on. They don’t sprout arms until they’re around 50 years old, so they’re a good reminder that in the great scheme of things, 50 is just not that old.DSC04932

 Very old saguaros are also very fragile, though. They store water in their trunks, so as they grow taller, they get very top-heavy, and they can be blown down in the winds that accompany our summer storms. If you look at the base of the young cacti in the photo above this one, you’ll see the skeletons of a previous generation lying at their feet.

Once in a while you’ll see one growing in a cristate form that scientists aren’t sure how to explain. Something happens to cause the top of the cactus to grow in many directions at once, fanning out from the trunk in a crest shape. There’s speculation that it’s caused by freeze damage or maybe a lightning strike, but nobody really knows. Cristate saguaros are rare, but Saguaro National Park is home to many. I didn’t see one today, though, so there’s much to look forward to for future visits.