The name Mt. Teshio-dake (天塩岳, Teshio-dake) is said to come from the Ainu word teshi, meaning ‘fish trap.’ Along the length of the river to which the mountain gives its name, there are a number of places where bedrock juts up above the waterline, and true enough, they do look like fish traps. This river, the Teshio-gawa (天塩川), starts on the slopes of Teshio-dake and winds far northward to empty into the Sea of Japan in the town bearing its name, making it the country’s fourth-longest river.
Besides the main summit, the Teshio-dake massif features a number of minor summits, namely, Mae-Teshio-dake (前天塩岳) and Nishi-Teshio-dake (西天塩岳). The three mountains together give the whole massif a characteristically slender and graceful form. In this guide you’ll follow a clockwise loop on the western flank of the massif, climbing up to Mae-Teshio-dake, over Teshio-dake itself, and connecting to Maru-yama (円山) peak, and descending back to where you started.
The trailhead is at the A-framed Teshio-dake Hut (天塩岳ヒュッテ, Teshio-dake hyutte), where there’s also a campsite. Staying at the camp or at the hut the night before the climb itself is a great way to set the mood for a weekend in the woods.
You’ll follow the stream called Gama-sawa for a little ways before reaching a junction with the connecting trail. The old trail end of the connecting trail (旧道側の連絡路, kyuudou-gawa no renraku-michi) climbs the long slope to your right and meets up at the top with a lesser-used new trail. You'll be coming down on the connecting trail a little later. the connecting trail junction (old trail side) , and then a little ways further on, the old trail junction (旧道分岐). From here you’ll leave the Gama-sawa and start the long climb up to Mae-Teshio-dake.
Before you reach Mae-Teshio-dake, you’re likely to see the withered, bone-white remains of some old dwarf stone pine—the result of an old forest fire. Around here as well a secondary trail will split off to the right and detour the summit along the mountain’s flank; but Mae-Teshio-dake claims incredible views and the end of the climb isn’t too hard. Just below the summit, you’ll cross a field of scree with Komakusa bleeding-heart growing here and there. It's not native to the mountain, which poses a serious problem for the native flora; but it is pretty.
From Mae-Teshio-dake you’ll head down into a col along a ridgeline and turn towards Teshio-dake proper. When you come to the junction where a trail merges from the eastern flank of the mountain, it’ll only be a little ways further to the summit of Teshio-dake. Looking out over the multilayered ridgelines to the south, you should be able to see the gleaming snows in the valleys and ravines of the Daisetsuzan (大雪山), far off in the distance. To the north, the characteristically low and quiet mountains of Northern Hokkaido will stretch out over the horizon.
From the summit you’ll descend via the new trail. Along the dwarf stone pine-covered ridge you’ll also see some smaller flowers—yellow-flowered rhododendron, crowberry, and lingonberry. Shortly thereafter, the pine will give way to a field of sasa bamboo and you’ll arrive at the Nishi-Teshio-dake Hut (西天塩岳ヒュッテ, Nishi-Teshio-dake hyutte). It’s another tough old A-frame, somewhat older than the one at the foot of the mountain, with a toilet standing alongside. If you're feeling keen, there's an old trail up to the summit of nearby Nishi-Teshio. It's a great spot for lunch on a quiet day.
As you put distance between Teshio-dake’s handsome shape and yourself, you’ll climb over the round, flat-topped Maru-yama and down into the forest. You'll descend into the gnarled, peeling arms of the Erman's birch—a beautiful spot in the late summer and early fall when the leaves go bright yellow.
When you reach the junction at the new trail end of the connecting trail (新道側の連絡路, shindou-gawa no renraku-michi), head right. You'll trade the brightly-coloured Erman's birch for dark Ezo spruce as you descend the winding, rocky trail. At the bottom of the valley you'll reach the old Gama-sawa. Head left and follow it out the way you came in.
In June and July there will still be a good amount of snow, which makes the new leaves on the Erman’s birch that much more beautiful. Along the ridgelines you should see yellow- flowered rhododendron, Matsumura cinquefoil, and alpine bearberry. Snow will probably remain around Nishi-Teshio-dake Hut, until mid-July, so you can rehydrate on the runoff. The leaves start to turn red around mid-September; at this time as well, the first frosts will appear.