Cerastium brachypetalum

Cerastium brachypetalum, commonly called gray chickweed, grey mouse-ear or gray mouse-ear chickweed, is a spring blooming annual plant species. It is native from Eurasia and introduced and naturalized in North America.
"Cerastium brachypetalum" is one of 101 species deemed high priorities for conservation in the UK by the wild flower and plant charity Plantlife.
References.
Milne-Redhead E. "Cerastium brachypetalum Pers in Britain" The Naturalist July Sept 1947: 95-96
Horn Peter C. "Cerastium brachypetalum in decline in Bedfordshire" BSBI News 65 18:20 (1994)
Horn Peter C. "The Decline and Conservation of Cerastium brachypetalum in Bedfordshire"
The Bedfordshire Naturalist 48: 102 (1994)
Palmer J.R. "Cerastium brachypetalum - Status in West Kent" BSBI News 65: 21-22 (1994)
Horn Peter C. "Cerastium brachypetalum in a Bedfordshire Railway Cutting" BSBI News 
101 25-26 (2006)