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Plant Focus

Quercus macdougallii
A rare oak endemic to the Sierra Juárez in Oaxaca

2022 Post-Conference Tour: Arizona

3–6 September 2022

After the close of an energizing three-day Conference in Las Cruces, 18 of us led by our intrepid guides, Sean Hogan and Ryan Russell, loaded into vans and headed west for a four-day adventure in Arizona. We covered nearly 1,500 miles during our travels across the state, spending time in the deserts, chapparal, and forests that are to be found in the diverse landscape of Arizona. We saw 10 species of oaks and countless hybrids and were able to collect acorns from all but a few.

Our first stop was the Chiricahua Mountains in the southeastern corner of the state. As we approached the mountains, we could see the results of an exceptional summer monsoon season. The roads were lined with waist high grass waving in the wind and the distant hillsides were shining in a shade of emerald-green not often seen in Arizona.

Chiricahua National Monument
Rhyolite hoodoos in Chiricahua National Monument; these rock formations were carved by ice and water from layers of volcanic ash-flow tuff blown out by volcanic eruptions
© Roderick Cameron

We arrived at the Chiricahua National Monument visitor center at mid-day and met up with Darin Jenke, who would serve as our local guide throughout the Tour. It was clear that Darin knew this terrain well and had pre-scouted all the stops in advance of the Tour. With his detailed knowledge of the Arizona flora, along with the expertise of Sean Hogan, our group was never without an answer to the many questions that arose during the trip.

We enjoyed lunch in a picnic area along a creek surrounded by Quercus emoryi, Q. arizonica, and Q. hypoleucoides. It was a peaceful scene interrupted only by the raucous calls of the Mexican jays (Aphelocoma wollweberi) that would occasionally take a break from caching acorns to swoop in and try for a scrap of food that may have fallen from our table.

Mexican Jan
A Mexican jay (Aphelocoma wollweberi) at Chiricahua National Monument © Bryan Denig

After lunch, Darin led us up the mountain road to Echo Canyon trail, where, on a brief hike, we observed the compact Q. toumeyi growing alongside manzanita (Arctostaphylos pungens and A. pringlei) and a beautiful little red Penstemon pinifolius.

We couldn’t stay long in the Chiricahuas as we needed to make it to our next stop before dark: the Santa Catalina Mountains and the highway to the top of Mount Lemmon. After a two-hour drive west, we began our climb up above the desert floor, giving us a view of the city of Tucson spread out below. It was amazing to see the flora change as we steadily climbed more than 5,000 feet. At the base of the mountain, we left stands of saguaro cacti (Carnegiea gigantea) and palo verde trees (Parkinsonia microphylla and P. florida), passing through oak-pine woodlands and ultimately reaching fir (Abies sp.) and aspens (Populus tremuloides) at the top. At about the midway point we stopped to find a stunningly beautiful Q. oblongifolia shimmering in striking silvery-blue color along the edge of a creek; alas, the acorns on this tree were far from being ripe. Darin informed us that this species is one of the last to produce mature acorns and we would need to come back in December to collect them. I just might be willing to make the 2,000-mile round trip drive from my home in Texas to collect acorns from this special tree.

Quercus oblongifolia
Quercus oblongifolia near the Mt. Lemmon highway © Sairus Patel

We finished the climb to the top, where we found Q. hypoleucoides, Q. gambelii, and Q. rugosa. By this time the sun was below the horizon, and we scrambled in the fading light to gather a few acorns before we loaded in the vans to head to our hotel in Tucson.

The next morning, we headed north past Phoenix for the climb up appropriately named Oak Creek Canyon, where we would see Q. emoryi, Q. gambelii, Q. hypoleucoides, Q. grisea, and Q. turbinella. The road followed the canyon up to the edge of the Mogollon Rim passing through the red rocks of Sedona along the way. This is one of the most beautiful roads in Arizona and, not surprisingly, it turned out to be popular destination on a Labor Day holiday weekend. After finally getting past the crowds, we reached the rim, where we had a spectacular view of the canyon below in near solitude.

Oak Creek Canyon
View of Oak Creek Canyon from edge of the Mogollon Rim © Bryan Denig

The quiet contemplation of the view came to an end quickly though as Darin pointed out the interesting oak hybrids that were growing just below our feet and we all began to collect acorns. This location on the rim of the Mogollon Plateau is an ideal place for hybridizing events as the prevailing wind blows pollen up the canyon from the lower elevation Q. turbinella and Q. grisea to the high elevation Q. gambelii. I was particularly excited to collect a blue-leaved hybrid with a leaf morphology intermediate to Q. turbinella and Q. gambelii. This beautiful small oak will have a place of honor in my home garden. (Side note: I checked the acorns just before writing this article and noticed that they all have germinated. Hooray!).

Quercus turbineela x gambelii
Quercus turbinella × gambelii on the Mogollon at Oak Creek Canyon © Wally Wilkins

We ended the day in Flagstaff, where we enjoyed a cool, breezy evening at 7,000’ elevation. This was a nice break from the heat of the desert below that we would experience again in full force in the coming days.

The next morning we were off to the far western part of the state, where we would visit the isolated Hualapai Mountains. Here we found Q. palmeri and Q. chrysolepis, section Protobalanus oaks that are typically associated with California and its Mediterranean climate, but which reach the easternmost extent of their range in Arizona. It was my first time seeing Q. palmeri and as I reached out to touch the tree, I painfully realized that one of the distinguishing characteristics of this species is stiff spiny leaves. Ouch! You need to be careful around this oak.

Quercus palmeri
Quercus palmeri in the Hualapai Mountains © Wally Wilkins

We left the Hualapai Mountains heading back toward the central part of the state and our ultimate destination of Prescott. Along the way, we passed through a forest of Joshua trees (Yucca brevifolia) lining both sides of the highway. These 10-15’ tall multi-trunk yuccas in Arizona are similar in size to those seen in the Joshua Tree National Park in California but are much bluer in color, creating a stunning landscape.

As we climbed up the winding road from the desert floor towards Prescott, the hillsides became densely covered in oaks, first primarily Q. turbinella then shifting to a mix of Q. emoryi, Q. arizonica, Q. grisea, and Q. gambelii. We stopped just before town in the fading early evening sunlight to collect acorns.

Quercus turbinella
Observing a large Quercus turbinella near Tortilla Flat © Bryan Denig

On our final day of the trip, we headed towards the Superstition Mountains east of Phoenix. After a scenic drive along the Apache Trail highway and Canyon Lake we reached our destination of Tortilla Flat. Darin took us to a population of Q. turbinella growing along the edge of the creek. Many of these trees had characteristics of Q. ajoensis, and Darin felt this might be an additional population of these rare oaks outside of the range identified in the southwestern part of the state. Unfortunately, we were in the midst of a late season heat wave and the temperature was well above 110 °F, so we opted to limit our hike and head back to the vans, where dripping with sweat we posed for a final group photo.

Group photo
Searching for shade as a respite from 110 °F temperatures © Roderick Cameron

A detailed Tour report will be published in the 2023 issue of International Oaks (Proceedings of the 10th International Oak Society Conference). IOS members can view more photographs of this Tour in a photo gallery here.