Oze National Park

Ozegahara is a raised bog at about 1,400 metres, the largest high-altitude marsh in Honshu, formed when lava dammed a valley and the basin filled with peat over thousands of years. It is crossed by around twenty kilometres of wooden boardwalk, and stepping off it is prohibited - the peat surface takes decades to recover from a footprint, and the boardwalk system, maintained and replaced plank by plank, is why the marsh still looks as it does. Two flowerings define the season: mizubasho, the Asian skunk cabbage, comes up in white spathes across the marsh in late May and early June as the snow retreats, and nikkokisuge, a day lily, turns the Ozenuma shore yellow in July. Autumn turns the whole basin copper in late September. Access is deliberately restricted - private cars stop at outer car parks and the last stretch is by bus or on foot.

What you actually see

• Twenty kilometres of boardwalk - the only permitted surface across the marsh.
• Mizubasho - white skunk cabbage spathes coming up as the snow retreats.
• A raised bog at 1,400 metres - the largest high marsh in Honshu.
• Restricted access - private cars stopped well short, the last stretch by bus.

When to go

Late May to June for mizubasho; late September for the copper marsh. Two days.

Honest expectations

Access takes hours and involves buses and a walk in from the pass. The marsh is snowbound roughly November to April. Weather at altitude changes fast and there is no shelter on the boardwalk. Mountain huts must be booked and are basic.

Nearby

Katashina village is south; Aizu is north across the mountains.