Scarlet pimpernel Anagallis arvensis

Best time to see: mid May to mid Oct

Key facts

A creeping annual with five-petalled flowers, usually pale scarlet, sometimes pink or blue

Also known as poor man's weatherglass because its flowers open only on sunny days, roughly from 8 am to 2 pm

A weed of cultivated fields and on bare ground

Extras

Pairs of unstalked, pointed oval leaves grow along the stems