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Oze NP, Gunma
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The usual story says sword-shaped Kin-kōka leaves were mistaken for iris. But botanist Shinayuki Suto recalled hiōgi-ayame blooming by Ayamedaira’s ponds in the 1960s and argued the flowers may explain its name.
Before boardwalks, hikers could roam freely over the mire. After buses began reaching Fujimishita in 1957, crowds followed this main gateway to Ozegahara, trampling about 1.2 hectares bare—over a tenth of Ayamedaira.
Kin-kōka’s yellow, star-shaped flowers open upward along each stalk, usually peaking in late July. By autumn, the same plant’s blade-like leaves turn vivid orange across the marsh.
Peat-block transplants failed to spread, so restorers switched to contour wood barriers, Mitakesuge sedge seed and straw mats to hold the peat in place. By 2008, about 90% of the bare ground had greened over.
Unlike Ozegahara’s bowl-shaped wetland, Ayamedaira sits on a broad ridge: rain and especially winter snow supply most of its water. Its slope also lets meltwater carry peat downhill.
In restoration plots, where sphagnum covered at least 40% after 3 years, herbs covered more than 60%. The moss helps keep the peat moist and stable, giving other wetland plants a better chance to establish.
Peat cores show Ayamedaira’s ridge holds 1–1.2 m of peat. Volcanic-ash layers indicate an average buildup of just 0.23 mm a year since the mid-6th century—roughly 4 years for each millimeter.
Katashina’s women’s association helped collect Mitakesuge seed in Ozegahara for Ayamedaira’s early restoration. From 1992, the Oze mountain-hut association also joined the seed-gathering effort.
