What are Britain’s national flowers?

The national flower of England is the rose. The flower has been adopted as England’s emblem since the time of the Wars of the Roses - civil wars (1455-1485) between the royal house of Lancaster (whose emblem was a red rose) and the royal house of York (whose emblem was a white rose). The Yorkist regime ended with the defeat of King Richard III by the future Henry VII at Bosworth on 22 August 1485, and the two roses were united into the Tudor rose (a red rose with a white centre) by Henry VII when he married Elizabeth of York.
The national flower of Northern Ireland is the shamrock, a three-leaved plant similar to clover which is said to have been used by St. Patrick to illustrate the doctrine of the Holy Trinity.
The Scottish national flower is the thistle, a prickly-leaved purple flower which was first used in the 15th century as a symbol of defence. The three flowers - rose, thistle and shamrock - are often displayed beneath the shield on the Royal Coat of Arms.
The national flower of Wales is usually considered to be the daffodil, which is traditionally worn on St. David’s Day. However, the humble leek is also considered to be a traditional emblem of Wales, possibly because its colours, white over green, echo the ancient Welsh standard.