For more than a century, the Arnold Arboretum of Harvard University has conducted plant collecting expeditions across the temperate world to study biodiversity and amass a first-rate collection of trees, shrubs, and vines in Boston. This autumn, the Arnold Arboretum resumed this historic work with a collecting expedition to Japan, resuming international field work for the first time since the global pandemic. The two-week trek through forests across seven Japanese prefectures yielded 20 species of woody plants representing important research and conservation targets for the Arboretum.

The expedition was planned and organized by the Arboretum’s assistant curator Miles Schwartz Sax, who joined Keeper of the Living Collections Michael Dosmann on the journey. Starting off in mid September, Michael and Miles were joined by Mineaki Aizawa, Associate Professor in the Department of Forestry at Utsunomiya University and undergraduate student Yoshinari Hata. This expedition marks the Arboretum’s fourth collaboration with Professor Aizawa and his team to study and collect from Japan’s native biodiversity as part of the Arboretum’s Campaign for the Living Collections. This 10-year initiative seeks to accelerate the Arboretum’s efforts to document, collect, and preserve plants—particularly those of conservation concern—to help scientists address global challenges over the next century. The Campaign’s list of targets—or Desiderata—consists of nearly 400 species of woody plants representing various goals for enhancing the collections, including more than 150 species that have never grown before at the Arboretum.

Japan has an astonishing amount of plant diversity and has attracted Arboretum plant collectors for more than 130 years. This long-term relationship has made the institution a rich repository of germplasm from Japan, with plants of Japanese provenance ranking third in the Arboretum’s collections behind the United States and China. Michael shared several posts on Facebook and Instagram during this trip to enhance these collections, which are compiled here along with some of his photographs from the field. Along with collections of seeds, herbarium specimens, and extensive written documentation, these photographs provide a visual record of this trip and its collections that will become part of our expeditionary archives.

September 20: Dispatch from Yamanashi and Gunma Prefectures, Honshu

Shojigataki Falls in Honshu Prefecture
Miles Schwartz Sax (left) displays his haul of Acer carpinifolium seeds as Yoshinari Hata (right) and Mineaki Aizawa (background) look on
Michael Dosmann stands in front of a massive specimen of Cercidiphyllum japonicum, the katsura.
Miles Schwartz Sax measures a massive katsura the team encountered, recording its circumference as 5.2 meters

Great collecting these past few days in Honshu!

Gorgeous Shojigataki Falls, the backdrop for collecting Acer carpinifolium (hornbeam maple) today. Mineaki, Miles, and Hata were quite happy with the bundle of seeds plucked from this fascinating maple. I could not help but admire a huge, upright Cercidiphyllum japonicum (katsura tree) just off the trail on the way up to the falls. It came in with a circumference of 5.2 m. It was a giant at some 25 to 30 m in height.

From the super tall, to the rather small….the other day, at Tambara Highlands in Gunma, we collected Mitchella undulata. Its bright red fruits stood out against the deep green leaves, making them easy to spot.

So far, we’ve made about a dozen seed and voucher collections over three days, including the Acer and Mitchella above, as well as Syringa reticulata (Japanese tree lilac), Deinanthe bifida (two-lobed false hydrangea), Viburnum sieboldii (Siebold viburnum), Eubotryoides grayana, and more!

September 26: Dispatch from Miyazaki Prefecture, Kyushu

The grooved, somewhat peeling bark of Tilia kiusiana, the Kyushu lime
Leaves and fruit of Tilia kiusiana, cut for the preparation of an herbarium voucher
A handful of seed of Tilia kiusiana
A fern-covered specimen of Tilia kiusiana stands out amid a dense forest of oak and bamboo

Another great day in the field!

Today’s journey took us to Kanto Mountain, in north central Kyushu, in search of a fascinating linden tree: Tilia kiusiana (Kyushu lime).

We found 18 trees growing in a forest dense with huge oaks (Quercus gilva) and bamboo (Phyllostachys edulis). Not much light got through to the understory, and what little seedling regeneration of trees (the linden, as well as other trees) gets eaten by wild boar and deer. The 18 trees we found were decades old, the oldest perhaps 75 to 80 years old.

Known for narrow leaves and grooved, somewhat peeling bark, this species stood out among the others once you got a search image for it. Also, almost all the trees’ bark was home to a small climbing fern, Lemmaphyllum microphyllum.

We made seed collections from several trees, plucking the small nutlets from cut branches, as demonstrated by Hata and Miles [see image at top]. We also gathered fruit from the ground, but kept it separate lest they be infested.

Beware the giant Joro spiders (Trichonephila clavata) whose webs were often strung between the boles! These were 2-3 inches across!! At least we didn’t find land leeches or mamushi vipers.

September 28: Dispatch from Tochigi, Honshu Prefecture

Expedition participants trek through Utsunomia University research forest in Funyu, Japan
Stand of Zelkova serrata, the sawleaf zelkova, one of the expedition targets
The green fruits of Buckleya lanceolata, the lance-leaved piratebush, are topped with wings
The green seeds of Ostrya japonica, the Japanese hop-hornbeam, are held in hops-like pillows

Final day gathering and hunting.

Yesterday we collected in the Utsunomia University research forest in Funyu. Some good hikes and scrambling up 75 degree slopes gave all of us a great workout.

We collected seeds from some broadly spreading Zelkova serrata (sawleaf zelkova), whose elephantine bark peels off in reddish-orange patches.

The odd hemiparistic plant Buckleya lanceolata (lance-leaved piratebush) was the find of the day. While the genus (including a species in the US) is fully able to photosynthesize to produce sugars, it also produces specialized roots that puncture the roots of neighboring species, stealing the odd nutrient or two. The shrub’s green fruits were topped with 4 wings. Perfect for playing badminton!

The towering Ostrya japonica (Japanese hop-hornbeam) had some exquisite, peeling bark and wonderful green seeds tucked away inside the little brown pillows.

We were never alone. Land leeches, chunky mamushi pit vipers, ticks and spiders kept us company (and on our toes).

All worth it though, with dumplings being the perfect dinner reward for Miles and me.

Now, a few days cleaning seed!!!

September 30: Dispatch from Utsunomia University, Tochigi Prefecture

Seeds of Stewartia serrata
Seed of Buckleya lanceolata
Cleaned and packaged seeds from the expedition, ready for shipment to the Arnold Arboretum
Seeds boxed for shipment to the Arnold Arboretum.

And, that’s a wrap!

After several days (and nights!) of seed cleaning, Miles and I got all the collections processed, packed up, and shipped off for inspection. We had diligent assistance from Mineaki and his students as well, so made efficient progress.

It looks like there will be no US Federal Government shutdown, thankfully, because the last thing we want is for the seeds to sit in boxes for weeks upon weeks. Fingers crossed!

This has been another great expedition, with a fantastic team from the Arnold Arboretum and Utsunomia University. I cannot wait to see all of these new accessions eventually growing in the Arboretum’s living collections. So many fantastic taxa, some old (Zelkova serrata), some new (Mitchella undulata), all with stories to tell for decades and hopefully centuries to come.