According to The Garden, March 2014: 10:
Poppy (Papaver rhoeas) seeds are being planted in ‘dozens of U.K.-wide projects to flower in time for the centenary of Britain’s entry into the [First World] was, on 4 August’.
The Centenary Poppy Campaign is promoted by the Royal British Legion and towns will be sowing poppies to transform roadside verges and public green spaces into ‘living memorials’ to those who died during the War. The Devon village of Northlew, which proportionately lost more young men than any other community, plans to plant a 20 mile ‘poppy avenue’, and major gardens which intend to participate include the Royal Botanic Garden, Edinburgh, and the Chelsea Physic Garden.

Metro of 29 April 2014 has a photograph of David Cameron, Prime Minister of the U.K., with primary schoolchildren sowing poppy seeds in the garden of his official London residence, 10 Downing Street.  ‘The Royal British Legion has sent seeds to every school to mark the centenary of World War I.’

Images: upper, Wiki Commons; lower, Figges Marsh, Mitcham, London Borough of Merton; 8 May 2014.