Water-pepper, Persicaria hydropiper, is a bitter tasting map-maker.
It is an inconspicuous annual plant, but it is useful to natural navigators.
It grows up to about 70cm or 2 feet tall, is slender with narrow unstalked hairless leaves. In late summer it has pale pink flowers in narrow spikes that droop at the end.
It tolerates partial shade, but prefers well lit places. It thrives in neutral to slightly acidic soil.
Both parts of its name yield clues. The pepper part comes from the bitter, acrid taste of its leaves, shoots and seeds. These can add flavour to foragers’ dishes, but it is only popular in Asia. It is cultivated in parts of Japan and China.
The bitterness protects the plant from grazing animals. (One of its historical common names was ‘arsesmart’, because it was once used to repel fleas in bedding, but managed to find its way into places it wasn’t welcome.)
The water part is more useful for navigators. It is found in damp or wet places: meadows, woodland edges and clearings.
I often find it alongside ruts: because these places allow light in and collect water (see photo below).
As a general sign of moderately wet places I find it often acts as a check. If I’ve been crossing relative dry ground, it is a sign that things have changed; it is time to tread carefully and tune to other signs of water.
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