Anagallis arvensis, the scarlet pimpernel, is the wild flower from which Baroness Orczy’s hero took his name. It is a small,weed growing to about 1 ft., usually with bright scarlet , although the colour varies. It is also called the ‘poor man’s weather glass’ because the close temporarily when cloudy or wet weather is likely. (They also close in the afternoon, so this ‘test’ is hardly infallible!)
Anagallis linifolia is perennial in the wild but is best treated as anin gardens. There are blue, red and white forms, growing to about 6 in. Sow outdoors in April where they are to flower, avoiding cold, wet soils.