chapter 01
A Hidden Botanical Garden
Looking south from Atascosa Lookout towards the US-Mexico border. Smoke from the severe wildfires burning across parts of California, Oregon, and Washington begins to clear as day breaks. In the distance is Ruby Road, the main artery for vehicle access across the Atascosa Highlands.

A Hidden
Botanical Garden

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Chapter 01 - A Hidden Botanical Garden
The Atascosa Highlands are a series of five small mountain ranges located in Southern Arizona, which straddle the international boundary between the United States and Mexico. The 203,799 acres that make up the Atascosas are officially referred to as the Tumacacori Ecosystem Management Area, and are managed as a part of the Coronado National Forest.
Precipitous cliffs rise hundreds of feet from rolling valleys, creating a mosaic of varied microclimates that allow for species with wildly different habitat preferences to grow within a few yards of each other. This topographical variation defies traditional elevational life zone delineations, bringing habitat types together to form diverse ecotones where the lines between ecosystems blur.
Opuntia santa-rita (Santa Rita prickly pear) growing from exposed rock along a canyon running south through Cumero Mountain. This species is known only from Southern Arizona and Northern Sonora.
Archeological evidence suggests that the Atascosa Highlands were part of an overlapping boundary between the Hohokam and Trincheras cultures, long before the existence of the United States and Mexico.
The lack of significant perennial water sources suggests that indigenous communities probably had little in the way of permanent settlements throughout the Atascosa Highlands, but that the region would have been used for hunting and gathering, as well as movement between villages.
Anthropomorphic figures - oftentimes depicted with outstretched hands and fingers, or holding a bow and arrow - as well as abstract curvilinear, and representational designs depicting flora and fauna are some of the most common stylistic elements seen in Hohokam petroglyphs; thought to date back to A.D. 600 to 1450.
Indigenous use of the Atascosa Highlands is a chain stretching back across time. The links of which are formed by the numerous cultures which have found food and shelter in the rugged hills and verdant valleys of this region. While there has been little archeological work conducted on the Highlands compared to nearby areas like the Santa Cruz and San Pedro valleys; oral histories, mission records, artifacts, and archeological evidence offer glimpses into the lives of the people who have called these mountains home for millennia.
Hohokam petroglyphs at the peak of Cumero Mountain.
Hohokam bedrock mortars at the base of Cumero Mountain.
01/03 Agave harvesting knife, courtesy of the Tubac Presidio State Historic Park and Museum.
02/03 Worked stone sherds, courtesy of the Tubac Presidio State Historic Park and Museum.
03/03 Mano and metate, courtesy of the Tubac Presidio State Historic Park and Museum.
Randy Serraglio Conservation Advocate
You don't see a border, you see the opposite of a border. You see an endless, interconnected landscape. You see this incredibly rugged place where Mexico, U.S., those terms become irrelevant.
The grasslands of the Pajarito Mountains following a monsoon downpour. These summer rains spur the growth of heat and humidity loving plants that give the region a distinctively subtropical feel. The Arizona-Sonora Borderlands are in the midst of the most extreme long-term drought recorded in the region in 1,200 years which makes these monsoons essential to stabilizing drought-stricken ecosystems.
Jim Verrier surveying the hills above Holden Canyon in the Pajarito Mountains. Jim is a researcher and the Nursery Director of the Tucson based non-profit native plant nursery Desert Survivors, where he manages cultivation of native species for conservation and urban landscaping.
Myriopteris lindheimeri (fairy swords, hierba de la pena) in the Pajarito Mountains. This diminutive fern can form dense clonal colonies on shaded slopes.
Myles Traphagen Borderlands Program Coordinator for Wildlands Network.
It’s where everything’s converging, it’s the place where the jaguar and the black bear share the same trail, and you go further north and that ends, and you go further south, and that kinda ends but right where we’re at, right here, is where you see something happening
Echinargus isola (Rearkirt's blue) nectaring on Heliomeris longifolia (long-leaf false goldeneye). These tiny butterflies have a wingspan of less than an inch but can occur in vast numbers following abundant monsoon rains.
Coryphantha recurvata (Santa Cruz beehive cactus) at upper Alamo Canyon in the Pajarito Mountains. The only known locality for this small cactus in the United States, is in the Atascosa Highlands, where it grows on rocky ledges or tucked among bunchgrasses. Historical slide photograph courtesy of Frank Reichenbacher.
Ecologist and Ethnobotanist, Gary Nabhan at his home in Patagonia, AZ. Gary has been instrumental in establishing the Wild Chile Botanical Area in the Tumacacori Mountains to preserve populations of Capsicum annuum var. glabriusculum (chiltepin). These plants are the wild progenitors of dozens of chile cultivars including Bell, Anaheim, Serrano, and Jalapeno peppers.
Chiltepin is the port of entry, or the gateway drug to get people excited about the whole area. It's possibly...the northernmost wild Chile population that we know of in North America.
Gary Nabhan Ecologist and Ethnobotanist
All of our crops in the United States, have a narrow genetic base upon which the major varieties are constituted...the only way to get around that, is looking deeply at the history of the wild ancestors of those plants.
A rugged drainage hosts a previously undocumented population of Chiltepins a few hundred yards north of the Arizona-Sonora Boundary. These wild chili peppers - growing near the edge of their range - possess unique traits which could help plant breeders increase the resiliency of cultivated pepper plants
The fruits of chiltepins are relished by bird species who are unperturbed by the intense spice of these small peppers. This makes chiltepins an important seasonal food source for native avian fauna who spread the seeds to favorable locations to germinate.
Rancher, Sue Chilton harvests chiltepins growing in her garden near Arivaca, Arizona. These plants were grown from seed collected in the mountains nearby and easily withstand the extremes of heat and cold experienced in the area.
Leslie Goodding Botanist, 1946
If you care to wander down to the southern border of Arizona, following the unsurfaced road indicated on the sketch map here, you will find, in a neglected nook called Sycamore Canyon, a remarkable botanical garden in which the agencies of nature have been the only planters. In this nar­row, precipitous ravine, extending scarcely five miles from north to south, plants from the tropics and species from the north combine with other rarities, as in a man-made garden, to present a pattern of vegetation that is unique
Sycamore Canyon in the Pajarito Mountains. This canyon is an essential migratory corridor for birds and mammals, and hosts plant species that occur nowhere else in the United States.
Mimosa grahamii (Graham’s mimosa) growing in Sycamore Canyon.
Mimosa grahamii (Graham’s mimosa)
Frank Reichenbacher's floral checklist from a trip to Sycamore Canyon in the Pajarito Mountains in September, 1980. Checklists such as this can help botanists compare changes in the species demographics of a given locality and are essential to developing an understanding of how ecosystems around us are changing over time.
Quercus emoryi (Emory oak) and Juglans major (black walnut) growing together at the entrance to Sycamore Canyon in the Pajarito Mountains. In 1946 the botanist Leslie Goodding referenced this exact oak tree in an article for the New York Botanical Garden writing, "if you wish to explore...you will probably park your car in the shade of a widely spreading Emory oak."
Graptopetalum bartramii (Patagonia Mountains stonecrop) can occur as individual plants, or in small populations perched precariously on rocky crevices in the shade of riparian canyons growing just a few inches across. The flowers of this small succulent bloom following the summer monsoons and are pollinated by small flies. Seeds are thought to wash down canyon in seasonal floods which leads to isolated populations spread out from one another with limited ability to cross pollinate. This pattern means that the die off of a single shaded tree, or the misplaced boot heel of a passing hiker could be the end of an entire population.
The Atascosa Highlands are part of a larger chain of “sky islands,” isolated mountain ranges which connect the peaks of the Sierra Madre Occidental of Mexico with the Rocky Mountains of the United States and Canada. This is an area of incredible biological diversity located in one of the most ecologically rich regions on the planet. These mountains bridge political boundaries, and act as essential migratory routes for wildlife; providing a home for plant and animal species which would not survive in the harsh deserts below.
Frank Reichenbacher's observation and collection journal from July 26th - October 19th, 1980.
Frank Reichenbacher's observation and collection journal from April 24th, 1989 - April 27th, 1993.
Historical slide photograph of Penstemon discolor (Catalina beardtongue) courtesy of Frank Reichenbacher.
Frank Reichenbacher processing botanical specimens on a folding table behind the trunk of his Nissan Xterra. For nearly 40 years, Frank has observed and recorded a single population of Penstemon discolor (Catalina beardtongue) just south of Corral Nuevo in the Atascosa Mountains.
The Penstemon discolor (Catalina beardtongue) population in the Atascosa Mountains is located approximately 90 miles or 145 kilometers from the nearest known population. Studies of these isolated individuals may help botanists uncover the evolutionary and biogeographic history of this uncommon species.
Frank Reichenbacher Ecologist
It’s the region, or a region, where species are forming, and are going to be forming. Where disjunct populations become isolated from parent populations, genetic mutations accumulate, populations diverge in some of their characteristics, and traits, and become new species. It’s just a fantastic natural laboratory in which evolution is unfolding before our eyes.
Agave parviflora (small-flowered agave) a state-listed rare plant known only from a handful of localities in Southern Arizona and Northern Sonora. This uncommon species occurs in isolated colonies separated from each other by miles. The yellow blooms are pollinated by native bee species, and the flower stalks are sometimes browsed by deer and cattle.
Agave parviflora (small-flowered agave) habitat in the Pajarito Mountains. This species doesn't compete well with other plants and prefers to grow on thin, rocky soils, which prevent grasses and shrubs from growing too densely. Agave parviflora was first described from a collection made in 1855 by Arthur Schott, a botanist with the US-Mexico Boundary Survey.
Historical slide photograph of Agave parviflora (small-flowered agave) habitat courtesy of Frank Reichenbacher.
Historical slide photograph of Agave parviflora (small-flowered agave) courtesy of Frank Reichenbacher.
Robert Villa observing a population of Agave parviflora (Small-flowered agave) hidden among tall grasses east of Atascosa Peak. Villa is a naturalist, research associate, and curator of the greenhouse and garden at the University of Arizona's Desert Laboratory on Tumamoc Hill in Tucson, Arizona.
Robert stops to make a note in his field journal on a trip to Sycamore Canyon in the Pajarito Mountains. In addition to his work documenting the flora and herpetofauna of the Sonoran Desert region, Villa is president of the Tucson Herpetological Society. He is most well known for helping raise awareness for the unsustainable, and inhumane use of Bufo alvarius (Sonoran Desert toad) venom as a psychotropic substance.
Robert Villa Naturalist and President of the Tucson Herpetological Society
…the Atascosa Highlands, has species that aren’t even found anywhere else in the United States, or in Arizona, or in any other Sky Islands. So that begs a lot of biogeographic questions, how plants and animals arrived to where they're at, through what geological, and evolutionary theaters…
Robert Villa holding a Diadophis punctatus (ring-necked snake). This species occurs across a broad swath of North America and thrives in the riparian canyons of the Sky Island region.
Historical slide photograph of Oxybelis aeneus (Mexican vine snake) courtesy of Frank Reichenbacher. This species is extremely rare in the United States and is an indicator of the subtropical influence on the flora and fauna of the Atascosa Highlands.
Thamnophis cryptosis (black-necked gartersnake) dipping into a seasonal stream in Sycamore Canyon in the Pajarito Mountains. These snakes occupy a variety of habitats and elevations but are most often found near springs and streams.
Thamnophis cryptosis (black-necked gartersnake) dipping into a seasonal stream in Sycamore Canyon in the Pajarito Mountains. These snakes occupy a variety of habitats and elevations but are most often found near springs and streams.
Looking west from Atascosa Lookout towards Atascosa Peak.
Lieutenant Nathan Micheler Member of the US-Mexico Boundary Survey describing the Atascosa Highlands in 1855.
Three days were occupied in traveling this short distance. The trail for the first two was over almost impassable mountains; massive rocks, and steep precipices constantly impeded…progress…and turned the party out of its course, making the route circuitous as well as hazardous, rough ascents were surmounted, steep ravines followed down, and deep gullies passed, the mules had actually to be dragged along. The soil is very rich, the vegetation is profuse and there is a fine abundance of grama grass, live oak, and occasionally cedar (juniper) are seen on the hills. Some strange specimens of natural history were found at this place.
Lagascea decipiens (doll's head) blooming at the base of Cumero Mountain. This species is only found in the United States in a small portion of Southern Arizona.
A steep canyon running towards the border from Alto Shumaker Tank in the Pajarito Mountains.
Despite the interest of many prolific biologists there has never been a comprehensive flora of the Atascosa Highlands until now. A flora is a snapshot of a region at a given time; carried out by recording observations, collecting botanical specimens, and depositing these at an herbarium so that they can be referenced by future researchers. Floras are an essential element of understanding the ecology of a region.
Wendy Hodgson is a Senior Research Botanist at Desert Botanical Garden, and one of the world's foremost experts on the genus Agave. Here she explains the history of an agave cultivar on the grounds of the Garden. Agave cultivars like this one are species that were intentionally selected for and cultivated by indigenous people as a source of food and/or fiber.
Entrance to the Ahearn Desert Conservation Laboratory at Desert Botanical Garden in Phoenix, Arizona. This state of the art research facility is home to a crucial seed bank for Sonoran Desert plants, where Garden scientists are working to protect species from changing environmental conditions and human impact.
Greenhouses at Desert Botanical Garden in Phoenix, Arizona. The Garden houses a collection of around 400 rare, threatened or endangered desert plant species with a focus on cacti and succulents. Collections like these ensure that the genetic lineages of rare plants survive so that they can be studied and cultivated for conservation purposes.
Collection and observation journal of Wendy Hodgson detailing one of her first trips to the Atascosa Highlands in September, 1985.
Knife marks left on a Ferocactus wislizeni (fishhook barrel cactus) from the harvesting of two ribs for processing into botanical specimens. These ribs are later dried and pressed, before being deposited in an herbarium. Because of the difficulty in collecting cacti and succulents these plants are generally underrepresented in herbaria.
Ferocactus wislizeni (fishhook barrel cactus)
Wendy Hodgson Senior Research Botanist and Herbarium Curator Emerita at Desert Botanical Garden
When we collect these (botanical specimens), we won't know, how they'll be used in 20 years from now, 15 years from now, 100 years from now, who knows, they'll be around, they should be around for centuries.
Wendy Hodgson observing and recording information about a flowering Agave palmeri (Palmer's agave) prior to collecting a specimen.
Wendy Hodgson overlooking the grasslands north of Cerro Del Fresnal.
Wendy Hodgson returning to her Desert Botanical Garden vehicle with an Agave palmeri (Palmer's agave) specimen for the herbarium.
Botanical specimens being prepared for long-term storage at Desert Botanical Garden's herbarium. Plants are pressed and dried, and treated with a range of chemical and preservatives, before being glued to herbarium sheets with a label and photographs. They are then digitally catalogued and officially accessioned into the herbarium's collection.
Folders of botanical specimens ready for processing in the herbarium.
Wendy explaining the proper collection procedure for cacti and agave while on a tour of the herbarium at Desert Botanical Garden.
Frank Reichenbacher Ecologist
You learn so much about the particulars, of a particular species, or a particular area, and then from that build a larger view of the earth and nature as a whole, life as a whole...you learn answers to big picture questions by studying the individual parts
Wendy Hodgson observing individuals of Mammillaria grahamii (fishhook pincushion cactus) and Mammillaria macdougallii (pancake pincushion cactus). These plants thrive in the rhyolitic cliffs which rise above the surrounding grasslands.
Mammillaria grahamii (fishhook pincushion cactus) at Desert Botanical Garden.
A butterfly in the genus Asterocampa lands on the spiny branch of a chain fruit cholla at the base of Cumero mountain. "Cumero" is a Spanish word for the tree known in English as Celtis reticulata (canyon hackberry) which is the food source for the larvae of these butterflies.
Cylindropuntia fulgida (chain fruit cholla) cutting ready to be pressed and processed into an herbarium specimen. The grasses growing around the cutting are primarily non-native species.
Riparian canyons, grasslands, and oak woodlands are the most recognizable habitats of the Atascosa Highlands. However, there is another habitat type which is sometimes overlooked in botanical studies, the anthropogenic biome. These are places where the dominant factor driving the ecosystem is human disturbance. From tiny stock ponds to large lakes created by damming up canyons, and from old mine sites to strips of land blasted and cleared for border wall construction. These “anthromes” are ground zero for the spread of disturbance loving and invasive species. The greatest change wrought by intensive human disturbance is often not the complete eradication of life but rather the introduction of different species demographics into the delicate balance that supports diverse native habitats.
Light spills across the dried up pools at the narrows in Sycamore Canyon during extreme drought. Seasonal pools like these have historically provided important habitats for amphibians and reptiles in the Atascosas such as Rana chiricahuensis (Chiricahua leopard frog). Herpetofauna are under increasing pressure from ongoing drought, competition from introduced species like Lithobates catesbeianus (American bullfrog), and chytridiomycosis, a fungal disease that has dramatically impacted frog populations globally. Efforts are underway by the Arizona Game and Fish Department to eradicate invasive populations of bullfrogs, and support the reintroduction of the native leopard frog here in Sycamore Canyon.
An Arizona Game and Fish Department vehicle parked along Ruby Road where it crosses Alamo Canyon. Game and Fish is tasked with the monitoring and conservation of native species as well as control of hunting in the state of Arizona.
Tom Jones, Amphibians and Reptiles Program Manager with Arizona Game and Fish scans for Lithobates chiricahuensis (Chiricahua leaopard frog) at Peña Blanca Spring. This small pool is man-made, fed by a small, underground pipe that runs from the nearby spring. An obstruction of that single pipe, could easily result in the evaporation of this critical habitat for herpetofauna. The Atascosa Highlands were historically home to Lithobates tarahumarae (Tarahumara frog), a species that has now been extirpated from the United States entirely.
Tom Jones holds the desiccated remains of a snake killed by traffic along Summit Motorway south of Atascosa Peak. Increased traffic on these roadways from recreationists, migrants, smugglers, and border patrol can negatively impact the herpetofauna of the Atascosa Highlands who have to cross these roadways or use them to sun themselves.
Tom Jones Amphibians and Reptiles Program Manager with Arizona Game and Fish
The habitats that these animals occupy now are largely human-constructed habitats like stock tanks, whereas historically they would have been in springs and streams, and through climate change or human activities some of those springs are gone.
Looking east towards Atascosa and Ramanote Peaks from Ruby Road. The grasslands of the Atascosa Highlands have been altered by centuries of cattle grazing and fire suppression. The rolling plains are dotted with trees and shrubs that are unpalatable to livestock and which have thrived in the absence of fire.
Pennisetum ciliare (buffelgrass) is a non-native grass, which was intentionally introduced to Arizona in the 1930's and has gone on to become one of the most destructive invasive plants in the Borderlands. Buffelgrass contributes to biodiversity loss and encourages catastrophic fires which damage fragile desert ecosystems.
Pennisetum ciliare (buffelgrass)
The Atascosas have been inhabited for thousands of years, but over the last few centuries human activity has begun to have a profound effect on this landscape. In a day, a bulldozer can undo the progress of centuries of natural selection, precipitating radical shifts in the flora which ripple out to all the plants and animals of the Atascosa Highlands.
Quercus rugosa (netleaf oak) is one of the less common oak species found in the Atascosa Highlands. The population of netleaf oak in Sycamore Canyon is growing at the lowest known elevation for this species.
Grassland and Oak woodland come together in a side drainage of Pena Blanca Canyon. Though ecosystems are often split and defined by elevational range, the complex topography of the Atascosa Highlands brings together different habitats which increases the local biodiversity present within a given area.
Water has carved ravines in a rubble flow that comes down from a recently constructed section of border wall in the Pajarito Mountains.
The remnants of oaks buried by the waste rock from border wall construction and road building in the Pajarito Mountains.
Robert Villa Naturalist and President of the Tucson Herpetological Society
If we have the ability to preserve something, and save something from our excesses, or our excessive footprint, and consumption, then we should. Because the rate of change is happening at a rate that we've never recorded before, by orders of magnitude.
Yucca "schottii" (mountain yucca) near the mouth of Sycamore Canyon in the Pajarito Mountains stands nearly 8-10' tall. This tree-like yucca is found in the wooded canyons of sky island mountain ranges along the US-Mexico boundary.
Yucca "schottii" (mountain yucca) partially buried in debris from border wall construction near USFS road 222.
Pseudognaphalium leucocephalum (white rabbit-tobacco)
Fouquieria splendens (ocotillo)
Opuntia chlorotica (pancake prickly pear)
Pinus discolor (border pine)
Agave palmeri (Palmer's agave)
Elionurus barbiculmis (wooly balsamscale)
Randy Serraglio Conservation Advocate
You look out over the Pajarito Wilderness and you see the folds of the landscape and you can't even count them all. It looks endless, and it kind of looks indestructible. It looks so vast, and intimidating in a way that makes you feel really small.
Newly constructed sections of border wall running across the Altar Valley, seen through a grove of Fouquieria splendens (ocotillo) at the base of Cumero Mountain. The recent push to build border wall in the Atascosas continued up until the close of the Trump Administration on January 19th, 2021.

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