Scarlet pimpernel
Lysimachia arvensis
Family · Primulaceae · Irritating
Toxic
The tiny brick-coloured flower that opens across fields and closes when the weather is about to turn. They called it the poor man's weatherglass, and it really works.
Where it grows
Fields and pasture · Roadsides and waste ground · Town and roadside
Also known aspoor man's weatherglass, red chickweed
In flower
How to tell it
Prostrate, with four-angled stems and opposite stalkless leaves. Small brick-red or blue flowers with five petals. They close in high humidity and late in the day.
What it is confused with
No dangerous lookalikes known in the Iberian Peninsula.
What it is for
None. It contains irritant saponins and has poisoned livestock, despite its harmless look. It is worth having as a weather reading, which is use enough for a walker.