Which two plants are national symbols of the UK?

The UK is a union of nations, and its symbols often reflect this diversity. The rose has been England's national flower since the Wars of the Roses in the 15th century, where the red rose represented the House of Lancaster and the white rose the House of York. When Henry VII, a Lancastrian, married Elizabeth of York, the Tudor rose, combining both colours, became a symbol of peace and unity, and the rose has remained associated with England ever since. The shamrock, a type of clover, is strongly associated with Ireland and Saint Patrick, the country's patron saint. Legend says he used the three leaves of the shamrock to explain the Holy Trinity. While the UK includes Northern Ireland, and therefore has strong ties to Irish culture, the other options are not relevant to the UK's national symbols. Cacti are associated with arid climates, and olive trees are more commonly linked to Mediterranean countries, neither having historical or cultural significance within the UK.