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In Japan this plant's leaves are used as a vegetable - these are from the cultivar, not the wild type which has a far more pungent taste. Wild waterpepper produces oils that cause skin irritation, and the many acids in its tissues, including formic acid, make the plant unpalatable to livestock. Young red sprouts are used as a sashimi garnish, and are known as beni-tade (紅蓼?, red water pepper). Though livestock do not eat the wild type, some insects do, giving rise to the Japanese saying Tade kū mushi mo suki zuki (蓼食う虫も好き好き?, Some insects eat water pepper and like it), which may be translated as “There is no accounting for taste.” or more narrowly “Some prefer nettles.”
The seeds of the water-pepper may be added to wasabi.
Read more about this topic: Persicaria Hydropiper