The triumph and anguish of plant collectors can often be summed up with a single word: timing. No matter how well an expedition has been planned, collectors often confront either empty capsules or immature fruits. At other times, however, the fates align. In September of 2017, we embarked with colleagues on a collecting expedition to Azerbaijan, searching for multiple species poorly represented in botanical collections. The Persian ironwood (Parrotia persica) was our primary target, and for this species, our timing could hardly have been more auspicious.
The Persian ironwood is an ornamental workhorse in the witch-hazel family (Hamamelidaceae) and is one of two species in its genus. Documented collections of Parrotia persica in public gardens tend to be from nurseries, and plants of known wild provenance are mostly sourced from populations in Iran. Although descriptions of the species’ range tend to focus on the Alborz Mountains in northern Iran, plants do not typically recognize geopolitical boundaries, and thriving populations of Parrotia also exist in areas of the Hyrcanian forest and the Talysh Mountains of southern Azerbaijan. The flora in these biomes is considered a relict of a forest type that was much more widespread before glaciation events in the Quaternary, starting around two and a half million years ago. The Talysh region, in particular, includes more than ninety endemic species.1 Herbarium vouchers for Parrotia indicate a disjunct population in the country of Georgia, but it is widely believed these specimens were planted.
In mid-September, our team departed the Azeri capital city of Baku and drove southward along the coast towards Lankaran. The trip had been organized by the Plant Collecting Collaborative, an organization consisting of eighteen botanical institutions, and our collaborators on the trip included Peter Zale from Longwood Gardens, Matt Lobdell from the Morton Arboretum, and Vince Marrocco from the Morris Arboretum. Vast agricultural fields dominate this landscape along the Caspian Sea, irrigated with the waters of the Kura River, which flows throughout the Caucasus region. Cotton, tea, grapes, and various citrus trees are the primary crops. Along the drive, we saw roadside plantings of Quercus castaneifolia, the chestnut-leaved oak, which was another one of our species of interest. These plantings were the first we saw of the species in the country. After a long and bumpy drive, we were met in Lankaran by Hajiaga Safarov, deputy director of science at Hirkan National Park. Hajiaga committed his career to exploring southern Azerbaijan, documenting the flora and fauna. He graciously agreed to guide us over the next three days and assured us that he knew of several populations of Parrotia persica in the area.
Departing from our hotel the following morning, Hajiaga led our team southwest of the city to the rural farming village of Az Filial. As we gained elevation, the paved highway soon ended, and we continued driving on a hard-packed, single-lane road. Cresting the top of a small hill, we suddenly found ourselves in the middle of Parrotia-dominant forest. Scant herbaceous vegetation existed under the canopy of these magnificent trees, a result of intense grazing pressure from the surrounding farms. We parked under the shaded canopy of ironwoods and began to hear tapping on the car’s roof, as though a light rain were passing over. The cloudless sky was not precipitating; the sound we heard was something much more miraculous.
Plants in the witch-hazel family exhibit a unique form of seed dispersal. As the capsules of Parrotia persica begin to dry, the exterior walls (technically the exocarp) shrink in size and begin to apply pressure to the seed, causing its forceful ejection. This method of seed dispersal—the so-called drying squeeze catapult2—was the source of the light raining sound. When we exited our vehicle, we witnessed small, black seeds bouncing off the roof and hood. In a marvelous turn of fate, we had timed our trip to document and collect Parrotia at the most advantageous time. Witnessing the forceful ejection of these seeds only added to the intrigue of the species. All hands worked quickly to obtain fruits that had not yet dehisced. We gathered several hundred capsules from throughout the population.
Diversity in the Wild
The Hyrcanian forests extend from southern Azerbaijan into Iran, wrapping around the southern coast of the Caspian Sea. In Azerbaijan, Parrotia occurs at elevations between sea level and around 1,600 feet (500 meters). Strong cultural influences of forest grazing, active felling of trees for firewood, and coppicing for fencing materials and winter feed have transformed the landscape. Farmers also coppice trees to minimize the shading of valuable meadow environments that provide winter fodder for sheep, cattle, and goats. The extensive coppicing in this region has made it difficult to see the natural habitat and variability of Parrotia. Examining the approximately fifty trees within the small population that we first encountered, it quickly became clear that an impressive amount of genetic variability was present. Bark characteristics alone were distinctly different, with variation including creamy, dappled camouflage mottling and golden, iridescent, paper-thin flakes. It was far too early in autumn to see any fall color in this population, but we suspected that variation might exist for this trait as well. After making another collection from a heavily fruited Caucasian zelkova (Zelkova carpinifolia), we departed from the site and headed farther south towards the Hirkan National Park.
Driving along the Lerik–Lankaran highway, we saw the Talysh Mountains begin to slowly build elevation as the forested areas became more dispersed between meadows and xeric terrain. Hajiaga was leading us to a historic cemetery and mosque outside the village of Babagil. In addition to Parrotia, our group was targeting several other unique woody species: the chestnut-leaved oak and a subspecies of the common boxwood that is endemic to southern Azerbaijan, Buxus sempervirens subsp. hyrcana. We encountered both species outside of the cemetery and mosque. This site dates to the sixteenth century and contains many enormous planted specimens of Caucasian zelkova and chestnut-leaved oak. Across the road from the cemetery is a remnant piece of the Hyrcanian forest. Here, we discovered large boxwood growing in the heavy shade of Parrotia persica. Just beyond the roadway, we encountered our first large specimens of the chestnut-leaved oak. They created a towering forest canopy over 65 feet (20 meters) tall, with trunk diameters reaching over 3 feet (1 meter). Unfortunately, these two species develop seed at the opposite ends of autumn; the boxwood had already dehisced, and the oaks were not yet ripe enough for collection. We were able to make a large collection of intact seed capsules from the Parrotia on the property. This collection, at 1,510 feet (460 meters), marked the highest elevation at which we found Parrotia growing, and it should make for an interesting evaluation for cold hardiness.
Departing westward, our group continued towards Lerik, a historic mountain town perched at 3,600 feet (1100 meters), overlooking the border with Iran. Gazing southward from the windows of our vehicles, we came across a magnificent sight: a sprawling forest of Parrotia persica filled the expansive valley beneath us. Towering velvet maple (Acer velutinum) dominated the upland areas, and enormous Caucasian alder (Alnus subcordata) were dotted along a slow-moving creek. Azerbaijan had been plagued in 2017 with a major drought, leaving the herbaceous layer completely dormant in autumn and adversely affecting the quality of autumn color. Despite this drought, the Parrotia in this valley showed deep hues of burgundy, red, orange, and yellow. Throughout this population, a diversity of form was also present. We noted many trees with dense conical crowns and a strong branching hierarchy. These structural characteristics would be well suited for trees selected for urban plantings. We were unable to access the forest because we had much more work ahead of us, but the memory of this valley remained with us after the trip.
A Return to the Valley
In late October 2019, the two of us traveled again to Azerbaijan to attempt collecting the chestnut-leaved oak from throughout its northern range. Similar to Parrotia persica, this species only occurs in the mountains of southern Azerbaijan and northern Iran. Its acorns don’t fully ripen until late in the season, and we hoped to collect them before they fell to the ground, where insects and herbivores can render them useless. The drive south from Baku to Lankaran took half of the time during this trip, as construction of a multilane freeway had been completed, connecting Baku to Tehran, Iran. Our failure to collect acorns from this rare oak had haunted us for the past two years, and we were eager to determine if we had properly timed our trip.
The landscape throughout southern Azerbaijan looked vastly different compared to 2017. Precipitation had fallen evenly through the year, and the previously dormant herbaceous layer was putting on an amazing show. The meadows surrounding the Babagil cemetery and mosque were filled with flowering geophytes. Two species of crocus (Crocus speciosus and C. caspius) carpeted the landscape and appeared almost as a monoculture lawn in areas that were heavily grazed. Pink-flowered cyclamen (Cyclamen coum) dotted the shaded understory of the endemic boxwood. The flowering spectacle was a wonderful sign of good seed development, and we were able to make three separate collections of chestnut-leaved oak at elevations ranging from 1,540 to 2,900 feet (470 to 900 meters). After finishing our oak collecting early, we had time to indulge in the forests of Parrotia persica.
As we drove along the highway from Lerik, back to our accommodations outside of Lankaran, we made a familiar stop to gaze across the valley of Parrotia that we had discovered two years before. Our timing was once again rewarded with amazing views of the valley in full autumn colors. It is difficult to describe the array of colors. Individual trees within the canopy exhibited shades of deep burgundy, brick red, orange, and buttery yellow. We decided to use our remaining day of the trip to attempt to access and document this population. We collected GPS coordinates and headed back to our accommodations to plan the next day’s work. After looking over various maps and satellite images, we were able to devise a way to drive as close as possible to the ridgeline across the valley, where several small houses stood. Our goal was to closely examine the trees in this population, taking photographs to document autumn color and differences in form. Trees with exceptional qualities would be geotagged so that we could return to them for propagation material in the coming years.
The following morning, we departed the hotel and headed towards the valley, excited by the prospect of getting to walk beneath the canopy of the relict forest. The paved road quickly turned into a dirt path, and after crossing over a shallow creek, it became a deeply rutted, muddy quagmire. Our translator and driver, Ilgar Guliyev, guided us through the terrain with expert precision. We soon found ourselves parked outside of a small farmhouse, and Ilgar went in to inquire about accessing the valley below the property. After a short conversation with the owners, we were informed that the valley belonged to the state, and our collecting permits would allow us access to the site. Basing our navigation on several massive chestnut-leaved oaks and oriental beech (Fagus orientalis) along the top of the ridge and a group of towering Caucasian alder at the bottom, we began traversing towards several Parrotia we had photographed the day before. The first selection that we documented exhibited a uniform, brick-red autumn color throughout the canopy. We continued to traverse up and down the steep slopes of the hill, documenting selections with peachy-pink autumn color, dense and pyramidal habits, and even dappled burgundy and green foliage. The diversity of the species within this singular valley was amazing to see. We hope to return to the valley in late spring to obtain scion wood from these selections to begin growing and evaluating their performance in various climates and conditions.
From the Wild, Into Cultivation
The study and documentation of plants in situ is a valuable means of determining species that are well suited for urban horticulture and other specific uses. In Lankaran, we were also able to see how Parrotia persica has been used locally in extensive urban plantings. The species could be seen in park environments as well as in small curbside planter spaces. The hot, dry summers of Lankaran coupled with challenging site conditions of urban environments did not seem to affect this highly adaptable species. As a street tree, the species often becomes too wide, resulting in unflattering pruning efforts, but this issue could be solved with more intentional selection. As we had observed, an extensive variation in the size and expression of Parrotia occurs in the wild, suggesting the fantastic development potential of the species for public plantations in both Europe and North America.
In cultivation, Parrotia is mainly represented by seed-propagated material, which results in large variations, making it difficult to predict mature size and habit. Presently, cultivars of Parrotia persica available on the market include ‘Vanessa’, ‘Ruby Vase’, and ‘Persian Spire’, which all represent narrow-growing forms. Based on our field observations, the species has significantly more expressions that deserve to be evaluated in cultivation. We hope to develop new cultivars of this species that will have uniform size and fall color characteristics. The species’ adaptability to periods of intense heat and dry soil conditions, coupled with its tolerance for high pH soils, makes it a perfect candidate for further development as an urban tree. Hopefully, we will once again be blessed with perfect timing to collect from these populations and continue working with this relict species.
Endnotes
1 Safarov, H. M. 2009. Rare and endangered plant species in Hirkan National Park and its environs. In N. Zazanashvili and D. Mallon (Eds.). Status and protection of globally threatened species in the Caucasus (pp. 193–198). Tbilisi: CEPF, WWF.
2 Poppinga, S., Böse, A. S., Seidel, R., Hesse, L., Leupold, J., Caliaro, S., and Speck, T. 2019. A seed flying like a bullet: Ballistic seed dispersal in Chinese witch-hazel (Hamamelis mollis Oliv., Hamamelidaceae). Journal of the Royal Society Interface, 16(157): 1–10. http://doi.org/10.1098/rsif.2019.0327
Acknowledgment
This work would not have been possible without the guidance and expertise of our partners at the Azerbaijan National Academy of Sciences, Institute of Botany and Central Botanical Garden of Azerbaijan, and the Hirkan National Park of the Ministry of Ecology and Natural Resources, Republic of Azerbaijan. Funding was generously provided by the Daniel F. and Ada L. Rice Foundation. Our work is dedicated in memoriam of Dr. Hajiaga Safarov (March 1, 1963–November 17, 2018).
Phillip Douglas is the director of plant collections for the Chicago Botanic Garden and also serves as the chair of the Plant Collecting Collaborative.
Henrik Sjöman is a senior researcher at the Swedish University of Agricultural Sciences and the scientific curator at the Gothenburg Botanical Garden.
Citation: Douglas, P. and Sjöman, H. 2021. Into the valley of Parrotia. Arnoldia, 78(4): 10–15.
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