Tsubaki mushroom. It is actually an aquatic plant, and when the water dries up in the fall and winter, the above-ground part of the mushroom dries up and the underground fruit is buried in the sludge. It is a seasonal vegetable that is only available in the fall and winter, and it has an early and a late maturity. Early-ripening zygomycetes are dug up this season, and late-ripening zygomycetes wait until New Year's Eve to go on sale.