August steamed hot as plant explorer Ernest Henry Wilson traversed the wilds of northwestern Sichuan in 1910, leading his fourth expedition to China. At this point in his career, many of the species Wilson saw were becoming familiar to his eyes, even mundane, and he was eager for something different. Although the expedition targeted conifers he observed on previous excursions, namely firs (Abies) and spruces (Picea), he was eager to see new habitats and with them, new species. On earlier trips, Wilson had visited Songpan—his destination—from Chengdu, Sichuan’s capital to the south, using one of two routes. The most direct option tracked the Min River north, though it was rather depauperate in botanical diversity. Wilson had also used a counter-clockwise route that bore him north-northeast of Chengdu through modern-day Mianyang and beyond to Pingwu (Longan Fu in his day), and then west-northwest to Songpan.
This time, he forged a way through an expanse few westerners save a couple of missionaries had braved before. The path cut between the previous routes and would provide him the opportunities he sought. On the outset of this trip’s leg, he did indeed encounter several things for the first time: he was robbed, from one of his own porters no less, and a local official dismissed his request for an escort through the unchartered territory.
This same region of Pingwu became the destination for the 2017 NACPEC (North America–China Plant Exploration Consortium) expedition, which Andrew Gapinski (Arnold Arboretum), Jon Shaw (Harvard Magazine), Kang Wang and Jian Quan (both from Beijing Botanical Garden), Huaicheng Li (Chengdu Institute of Biology), and I undertook from 15 September to 1 October, 2017. I had tracked Wilson’s footsteps several times in the past, quite literally during the 2014 filming of Chinese Wilson (a documentary produced by Central China TV), seeing towns, roadways, mountain views, and of course plants that he had also visited. However, this trip was more poignant, for I now bore the title of Keeper of the Living Collections; the title of Keeper used only once before at the Arboretum, given to Wilson in 1927.
During our trip, we endured roadways capsized during the season’s earthquakes and rains, and we got up-close-and-personal with terrestrial leeches that slink ubiquitously in these rich, mesic forests. On the morning of September 23, our team set out to explore one of the many mountain valleys near Si’er, an area Wilson referred to as Tu-ti-liang shan or mountain. Wilson had been awestruck by the herbaceous plants there, in particular the fingerleaf rodgersia (Rodgersia aesculifolia), which grew “in [the] millions.” “It was in the fruiting stage,” he noted in China, Mother of Gardens, “but when in flower the acres of snow-white panicles must have presented a bewitching sight. Nowhere else have I seen this plant so abundant or luxuriant.” In an adjacent valley the previous day, we had seen the same species, each of its coarse leaflets reaching nearly a half-meter (20 inches) in length. As enthralled with it as Wilson had been, we joyously made a collection.
As we ascended the valley on foot, marching along a roadway that was tumbling into the torrent below, we were impressed with the expanses of large trees to either side. We spotted dove tree (Davidia involucrata), several species of birch (Betula spp.) and gargantuan specimens of the multi-stemmed Chinese beech, Fagus engleriana. Giant panda, we learned from our guide, often overwintered between the stout boles of these very beech trees. Wilson’s 1907 collection of the beech from Hubei is the only representation at the Arboretum, and likely anywhere else. Thus, on our hike back down the mountain, we secured fruits of this and other species.
Wilson may not have recognized the heavily wooded landscape that we saw. He described this sparsely populated hamlet of Hsao-kou (now Xiaogou and depopulated) as having “… open, park-like slopes, quite unlike anything I have encountered elsewhere in China. Now largely denuded of trees these glades are covered with grass, and horses, goats, and pigs are raised here in some quantity.”
The lumberman’s axe and the herder’s livestock had eliminated many of the conifers Wilson had hoped to find in the area. However, on August 17, 1910, he enthusiastically noted an abundance of Cercidiphyllum japonicum (katsura tree) growing throughout the landscape. Although he had seen the species on his previous travels, he had never seen so many growing together. The intrepid explorer got busy with his vasculum, collecting herbarium vouchers. This collection (Number 4301) would represent the type of what he and Alfred Rehder later described as a separate botanical variety with pubescent leaves and follicles, Cercidiphyllum japonicum var. sinense.
Wilson reported trees up to 36.6 meters (120 feet) tall, and 2.1 to 6.1 meters (7 to 20 feet) in girth. Even amidst these giants, one specimen stood out for its enormity—not in height but in girth: it was multi-stemmed and hollowed in the core, yet 16.8 meters (55 feet) around, which would be a diameter of 5.3 meters (17.5 feet)! Words are not necessary to conjure what Wilson saw, for he memorialized the tree in a photograph. This exact tree was our destination for the day’s hike, and for me it glimmered with personal significance, because Cercidiphyllum japonicum had drawn me to China for the first time in 1999 and I considered this a bit of a reconnection. This was now my eighth trip to China, and perhaps a bit like my predecessor, I sought some reprieve from the mundane.
I imagine that due to the openness of the landscape 100 years ago, Wilson spied the specimen easily from the path. Yet, even after our team left the road and ascended the steep and muddy streambanks, dense woods left us completely blind to our target. We had to bushwhack through the brush, and upon arriving at last, we could do nothing but marvel. Like the forest around it, the tree had recovered over the last century. The specimen had been but 8 meters (25 feet) tall in 1910; it now stood over 20 meters (65 feet) in height, and the diameter of the largest stem was just under 2 meters (6.5 feet). The three massive, original basal stems remained, though showed considerable wear. The tree at Wilson’s time was probably coppiced repeatedly for firewood, and it had since rebounded by sprouting many new stem suckers. The ability of Cercidiphyllum to resprout following stress (age, drought, fire, coppicing) is well known. Assuredly this aged survivor had once been a single stem, hundreds of years before even Wilson photographed it.
Years later, Wilson recalled this visit to the tree in August of 1910, stating that it was actually the first time he ever saw the species in fruit. He added parenthetically, “Later I collected ripe seeds, and this tree is now growing in the Arnold Arboretum, where it promises to be quite hardy.” Technically, it would have been Wilson’s collecting team that acquired the seeds and fruiting vouchers that October, for on September 3rd, 1910, a few weeks after initially seeing this Cercidiphyllum, he was caught in a landslide that busted his leg in multiple places. Luckily, his steadfast companions carried him to Chengdu where he spent the remainder of the autumn recuperating, before returning to Boston in early 1911. Our 2017 team was lucky, too, for this huge Cercidiphyllum bore fruits, which we collected under number NACPEC17-020 (we also collected fruits from other trees in the population under NACPEC17-021). And, luckily, none of us broke an appendage.
Of Wilson’s 1910 seed collection, but a single tree grew in the Arboretum. It was sited on Peters Hill, just to the south of the summit’s present-day access road in an area then called “rare trees of the Arboretum.” Accession 7281*A was near an American beech (Fagus grandifolia, accession 22798*E) that remains to this day. This Cercidiphyllum had survived the brutally cold winters in the early- to mid-1930s, proving its hardiness. However, by 1946, for an undocumented reason, it was dead. The tree had previously yielded enough budwood to produce five additional accessions, and a grafted plant (accession 133-41*B), the last of its lineage, grew in the Cercidiphyllum collection off Meadow Road. It was alive in 1948, but died shortly thereafter when its base snapped off, likely due to graft-incompatibility.
In early November of 2017, just weeks after I returned from China and the Arboretum propagator sowed the seed, the first seedlings of both of our 2017 collections germinated with abandon. In a few years, it will be a privilege and a joy to reintroduce an exact Wilson acquisition to the collections. While no doubt some trees will go along Meadow Road and elsewhere, I think one should return to the spot near the Peters Hill Summit, for old time’s sake.
Wilson, E. H. 1929. China, Mother of Gardens. 408 pp. The Stratford Company, Boston.
Michael S. Dosmann is the Keeper of the Living Collections at the Arnold Arboretum.