Mt. Daisengen-dake (大千軒岳) is a mountain standing deep in the Japanese beech woods in the center of Matsumae Peninsula (松前半島, Matsumae-hanto). Standing at the far southern border of Hokkaido, it has a great view over the Tsugaru Straits (津軽海峡, Tsugaru-kaikyou), and, geologically and florally, it looks more like a mountain in Tohoku than one in Hokkaido.
In former times it was called Mt. Ukon-dake (鬱金岳, Ukon-dake, lit. 'Mt. Turmeric'), and in fact there was a gold mine here. When Christianity was being suppressed in the Edo Period, a number of Christian miners were executed on this mountain. At Sengen Plateau (千軒平, Sengen-daira) and at the Kanayama Guard House Ruins (金山番所跡, Kanyama-bancho-iseki) there are a number of crosses standing as memorial monuments to the miners killed here.
The name ‘Daisengen’, meaning ‘great one thousand houses’, likely comes from the number of buildings that stood alongside the gold-panning canal; or otherwise something to do with the Asama faith, a sect of Shintoism associated with the worship of volcanoes. There is one trail climbing the eastern flanks of the mountain from a trailhead along the valley of the Shiriuchi-gawa River (知内川, Shiriuchi-gawa), as well as two trails that climb the western flanks.
In this guide you’ll climb the Matsumae Old Trail (松前旧道, Matsumae-kyuudou) and loop around to descend via the Matsumae New Trail (松前新道, Matsumae-shindou). The Old Trail trailhead sits at the deepest part of a forest road following the Oyobe-gawa River (及部川, Oyobe-gawa) up into the mountains; this forest road eventually lets out at Ishizaki (石崎), a small village in Kami-no-kuni Town (上の国町, Kami-no-kuni-chou). If you’re looking at Google Maps, just follow Prefectural Route 607 (道道607号線, Doudou 607 gosen) from Matsumae and you’ll hit the trailhead eventually.
From the trailhead you’ll soon enter a quiet forest of Japanese beech. The shape of the branches is lovely, and the atmosphere of the forest is characteristically Southern Hokkaido. As you climb up the old trail, you’ll begin to mount the top of a ridge that stretches west from Mt. Nakasengen-dake (中千軒岳, Nakasengen-dake). Until the end of June there will likely be some snow here, and the sasa bamboo grows abundantly as well, so be careful not to lose the trail.
You'll reach the top of the climb at 844 meters above sea level, where you mount the slim back of a ridge and enter a forest of Erman’s birch. Over the low, gnarled branches of the trees, you should be able to see the summit. Here, you’ll pass Japanese fawn-lily, Japanese wood poppy, and short-stipule violet after the snow melts.
Skirt below the summit of Mt. Nakasengen-dake and you'll arrive at Sengen Plateau, where the Shiriuchi Trail will join yours. Here among the Matsumura cinquefoil, Narcissus-flowered anemone, and Thunberg’s fleabane, you’ll also see a large white cross, a symbol of the terrible act committed here hundreds of years ago.
From here on out it’s a relatively easy hike to the summit. You’ll walk across grassy fields with wide open views before coming, directly below the summit, to Sengen Water (千軒清水, Sengen-shimizu), a little spring where water flows merrily. That there is a spring at this altitude might give you a sense of how well the mountain holds on to water.
The view from the narrow summit of Daisengen-dake is, among the views of Hokkaido, clean and fresh and beautiful. On a clear day, you’ll be able to see Mt. Hakkoda-san (八甲田山, Hakkoda-san) and Mt. Iwaki-san (岩木山, Iwaki-san), among the lower peaks of northern Tohoku, over the Tsugaru Straits. It might become apparent at this height why some call the straits 'the salty river' (shoppai-sawa): the straits will seem so narrow you could almost reach out and touch Hakkoda.
The Matsumae New Trail descends along a ridge stretching northwest from the summit. Although it’s a well-groomed trail, you won’t find any water along it. Like the Old Trail, along the upper reaches of the trail you’ll find short-stipule violet and Jesoana primrose, while the lower portion of the trail winds through a quiet forest of beech. The New Trail lets out about 3 km down an old logging road from where you likely left the car, so enjoy the quiet walk back. The trees here are mostly the same Japanese beech as you saw on the mountain, but they'll be interspersed here with Japanese horse-chestnut and Japanese wingnut trees, so typical of Southern Hokkaido.
The Shiriuchi Trail takes you up a stream towards the top of the ridgeline, passing a number of historic landmarks along the way, making for a very different trail from the standard route. You’ll find the trailhead at the far end of a forest road following the Shiriuchi-gawa River (知内川, Shiriuchi-gawa). There is a toilet and campsite nearby, and you can collect water from the nearby stream.
The first half of the trail follows the Shiriuchi-gawa River through a forest of Japanese beech and Japanese wingnut; the lovely shapes of the branches make this a particularly pleasant walk. The blooming vegetation of spring is also quite moving. You’ll pass a spot called Sebato (狭戸), then head up the wide river plain; further along you’ll find a cross-shaped memorial and the remains of the Kanayama Guard House.
At Kanayama along the Shiriuchi-gawa River, mining was undertaking from 1617 to 1639. The gold miners here were exiles from the Edo Shogunate; in 1639, 106 of them, Christians, were beheaded on the mountain. The monument remains as an emblem of the violent religious persecution of those days.
From Sengen-ginza (千軒銀座), you’ll cross the Ginza-no-sawa River (銀座ノ沢, Ginza-no-sawa) and begin the climb up the top of a ridge. You’ll climb a steep slope up this ridge, through handsome beech trees, to Sengen Plateau.
There will still be snow on the ridgelines until late June. As the snow melts you’ll start to see Thunberg’s fleabane, short-stipule violet, Japanese wood poppy, narcissus- flowered anemone; from mid-summer into fall you should see plenty of Dumortier’s daylily and ligularia. The leaves start to change in mid-October.