The tiny flower is an emblem of Sir Blakeney in the novel The Scarlet Pimpernel written by Baroness Emma Orczy.
Source of plant
Diminutive annual, biennial, or rarely, short-lived perennial; stems to 50cm, quadrangular, slender, diffuse, creeping to ascending. Leaves to 18x10mm, opposite, sessile, glandular, margins scarious, ovate to lanceolate, . Flower in uppermost axils closing in dark or cold conditions; pedicels to 35mm, recurved in fruit; calyx to 5mm, divided nearly to base, lobes narrow-lanceolate, apiculate, not concealing corolla in bud; corolla to 1cm diameter, scarlet or white, lobes ovate to elliptic, entire or dentate or crenate, marginal hairs numerous. Fruit to 5mm; seeds 12-45. Europe.
USDA Hardiness Zone