Monsoonal Madness

We left northern New Mexico on August 4, heading towards the borderlands to look for plants dependent on monsoonal rains. On the way, we drove through Petrified Forest National Park to look for Parryella filifolia, a pea family shrub, which we easily located. Trees and shrubs can usually be identified even if not flowering or fruiting, so I would have thought we had very few woody genera remaining to be found. But this year we have seen about a dozen new ones: eight shrubs, three trees, and one vine. We camped for a couple nights on the Mogollon Rim in central Arizona, an area we have not explored much before, and enjoyed seeing Gray-collared Chipmunk and Red-faced and Grace’s Warblers.

Monsoonal rains are an annual feature in northwestern mainland Mexico and the adjacent U.S. The southeast corner of Arizona, the majority of New Mexico, and the Trans-Pecos (extreme western Texas) receive half of their yearly precipitation or more from these summer storms. Monsoons are extremely complex meterologically (link), but basically they result from arid uplands heating up more rapidly in summer than do the nearby large bodies of water, causing a pressure differential that creates winds that transport moisture from water to land. In the case of the North American Monsoon, the Mexican Sierra Madre drives the pressure differential, and most moisture comes from the Sea of Cortez (separating Baja from the Mexican mainland) and the Pacific Ocean. Monsoonal rains in the U.S. typically start in early July and end about two months later, but they are highly variable in duration and intensity. This year the rains started in late June and were above average (often several times average) in amount almost throughout the monsoonal region. This gave us an outstanding opportunity to look for native plants that typically flower in response to summer rains.

Our first destination was near Sells, AZ, about 60 miles WSW of Tucson. Ironically, we could not get there on our first try because a massive thunderstorm caused major flooding; good-sized trees and large rafts of debris were floating across the road at a wash! As compensation, while we retreated towards Phoenix, we enjoyed a long-lived, very intense double rainbow in which both arcs reached the horizon at both ends – very unusual! We made it through the next morning and found the Sonoran Desert to be vibrantly green and filled with flowers — at our first stop, we found eight new species of plants in a roadside area only about 10 yards wide and 100 yards long! I don’t usually end three sentences in a row with exclamation points, but that does give an idea of the excitement of arriving in fabulous Southeast Arizona during a major monsoon season.

The weather was so hot that we had to make several changes to our usual routine. (1) We had something to drink and took breaks in the shade every twenty minutes spent outdoors. (2) We dropped our normal goal of 10,000 steps per day (4 miles) to 7,000 steps, corresponding to half an hour less walking each day. (3) We stopped keeping food in our refrigerator because it could not maintain safe temperatures during the hottest part of the day. This problem was exacerbated each morning when we pulled cold drinks and ice blocks from the fridge, for the cooler we keep in the truck, and replaced them with warm ones. We ended up completely packing the fridge with drinks, using their high heat capacity for thermal ballast. (4) We did get some relief from the heat at higher elevations and during thunderstorms, which occurred most days, and were able to sleep well at night by running our fans. But the batteries drained pretty quickly with the fridge running non-stop and fans going all night, and our truck generator and solar could not keep up, so we had to stay in campgrounds with electricity about once every four nights to recharge. To put this in perspective, we have sometimes gone an entire year without having to do this!

We spent four days close to Tucson, visiting Tucson Mountain Park, the eastern half of Saguaro National Park, and the Santa Catalina Mountains (via the road to Mt. Lemmon). New plants and plant genera were encountered at a remarkable rate, reducing the time available for finding them in the field, because it took so much time to identify them. Arizona has a very old published flora (from around 1960), though some families and genera have been treated recently in the periodical Canotia, which is a help. Still, on average, keying Arizona plants is time-consuming, and it can be hard nailing down identifications without a cell signal to consult other sources.

August 11 – 13 found us in the Santa Rita Mountains, about 35 air miles SSE of Tucson. The first area we visited was the eastern end of Helvetia Road, where we had high hopes of seeing a new plant family, Bixaceae. Upon reaching the site, we quickly found our target, Amoreuxia palmatifida, Mexican Yellowshow, which had very interesting fruits, flowers, and leaves, though the yellow and red flowers were not fully open. In a small area on the same slope we quickly encountered two more new genera that had eluded us earlier in the year, so it was a very exciting stop! With Bixaceae finally in the bag, after years of anticipation, we have just four remaining native North American plant families out of 239. We then crossed the Santa Ritas from east to west via Box Canyon Road, which we had never taken before. This road traverses the steep south-facing slope of a scenic canyon, and goes through good Five-striped Sparrow habitat, which also has some interesting plants. We particularly enjoyed seeing Mariosousa millefolia, a species formerly classified as an acacia, which in the U.S. is only known from four counties. We finished up in the Santa Ritas with two nights camping in Madera Canyon, a famous birding destination, where we had Rivoli’s Hummingbird and Elegant Trogon.

Our next three days were spent close to the Mexican border, not far from Nogales. Tumacacori National Historical Park, with its Jesuit and later Franciscan mission, was interesting and yielded a rather rare and range-restricted genus, Sicyosperma, in the cucumber family. Ruby Road, which heads west of I-19, provides access to a number of outstanding areas, and we spent a couple nights camped along the road, near Peña Blanca Lake. One morning we paddled on the small lake to give our canoe some exercise, and were rewarded with: five species of dragonflies, including a striking new one, Mexican Amberwing; marvelous examples of a globular cactus, Mammilaria heyderi macdougallii, growing horizontally out of cracks in vertical cliffs; and vocal Brown-crested Flycatchers. We found five new plant genera before heading east of the interstate. We visited the San Rafael Valley, southeast of Patagonia, for the first time; it showed at its best with endless lush green monsoon-fed grasslands under towering thunderheads.

Continuing east, we reached Cochise County, the southeasternmost county in Arizona. We camped for a night at Parker Canyon Lake, where a nearby family of Coyotes partied relentlessly. We found three new genera near the lakeshore, and remarkably, along 50 yards of dirt track, starting from our campsite, we located eight genera that we had first seen sometime in the preceding two weeks! Monsoonal Southeast Arizona clearly represents a unique botanical intersection of time and place. We then turned our attention to the marvelous Huachuca Mountains, taking the memorable Montezuma Grade across the southern part of the range and camping for three nights at a stunning dispersed site in Carr Canyon, on the east side. When we reach camp, I will often set out Eileen’s chair in what I deem the best spot, considering shade, light angle, scenic view, etc., and she’ll take her evening coffee there. I did a particularly good job in Carr Canyon, because while it was still quite light, she glanced up from her Kindle to see an adorable Western Spotted Skunk in plain view, just seven feet away!! This is a really difficult mammal to find; I’ve encountered just one before, which Eileen missed, so it was especially good she saw this one. Despite extensive effort involving a thermal scope and peanut butter-coated Wheat Thins, I never did get to see the animal. Eastern Spotted Skunk is also genuinely hard to find; our only sighting ever was one that was raiding a small mammal live trap we put out in Florida (now that one liked peanut butter!). Eileen also caught up on a bird species I had seen, which she had not: Berylline Hummingbird, a Mexican species, which we found after about three hours of looking in Ramsey Canyon.

Our last major destination in Southeast Arizona was the Chiricahua Mountains. We spent a day in Chiricahua National Monument, where we came across a family of five Coatimundis, which is always a fun experience. Just as happened in June, we failed to find an uncommon shrub, Apacheria, but we enjoyed the hike to The Grottoes on the Echo Canyon Trail and saw a number of Mountain Spiny Lizards, a new reptile for us. We crossed the Chiricahuas on Forest Route 42, camping for one night at a favorite spot at 8260 feet elevation, where we can pick up a cell signal with our booster. We found six of eight target genera on the traverse, and encountered one new genus serendipitously, quite a haul! Four of the new genera were in Asteraceae, the sunflower family, which has exceptional diversity in this region. We got pinned down for several hours by a thunderstorm and wondered if we’d make it out of Cave Creek Canyon given its propensity to flood, but we had no problems.

One of the four plant families we’ve not seen in North America is Molluginaceae, the carpet-weed family. There is a diversity of opinion regarding whether the family is native in North America and if so, which species are native, and in which part of their range. The authority we use, the Biota of North America Program (BONAP), considers one species, Glinus radiatus, as native in Arizona and southern California. Most records in this range are on private property, because the best habitat for this species is the mud left by drying stock ponds. We had tried several times to reach locations from which this species was reported, to find our way blocked by No Trespassing signs. After the most recent failure, just before reaching the Chiricahuas, we checked out some older specimen data, and noticed a 15-year old record on public land. Visiting the site, west of Globe, AZ, would require backtracking about 4 hours. We decided to give it a try despite the drive, as the habitat still looked reasonable in satellite photos. When we got there we found drying muddy areas filled with annual plants of several species – but no Glinus. By the time we finished the search in scorching heat, we were ready to camp and relax, but that turned out to be difficult. We tried several organized campgrounds and dispersed camping areas, and each one had something wrong with it – wildfire damage, danger of flash flooding, dubious occupants, etc. We ended up retracing most of our route, and driving long after dark. I am afraid that my feelings for Molluginaceae, which were already pretty negative, hit rock-bottom after this experience.

In total, during the 21 days covered in this blog post, we conducted 44 genus searches, of which 29 (a high 66%) were successful. In addition, we found 14 genera serendipitously, for a total of 43 new genera, accounting for almost half of the 90 new plant species seen during this period. Adding in a new plant family, a new mammal for Eileen, and a new bird for her as well, it was a remarkable three weeks in one of our favorite places.