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Chubu-Sangaku NP, Nagano
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Near Happoike’s north-side benches, Happo-waremoko sends stamens 3–5 cm beyond its flower spikes. It grows taller than ordinary waremoko and is thought to be a natural hybrid with karaito-sō.
Snow pushes sediment into a hollow that becomes Happoike, a natural basin for rain and meltwater—not a built pool. It reaches about 4 m deep, and its clear water shelters Japanese black salamanders and forest green tree frogs.
Along the pond trail, 347 alpine-plant species thrive—including plants usually found above 2,500 m at lower elevations. Nagano researchers call this “vegetation inversion”; serpentine ground also preserves Ice Age plant holdovers.
When the wind settles, Happoike can reflect all 3 Hakuba Sanzan: Shiroumadake, Shakushidake and Hakuba-Yarigatake. The peaks appear twice—once on the horizon and again upside down in the water.
East of Happoike, the local Happo-takane-senburi blooms with pale-violet petals freckled dark purple. Each flower is just 7–10 mm across, and the plant’s flowering season is July–August.
The alpine-plant belt around Happoike—not the pond alone—became a Nagano Prefectural Natural Monument on August 20, 1964. In 1968, Nagano built the nature-study trail from Kurobishidaira to the pond.
