66732 GBRF The First Decade 1999 - 2009 John Smith MD passes the blackthorn blossom at Stoke Orchard, as it works the 6Z88 11:12 Peterborough to Cardiff Tidal scarp empties on 6 May 2013. Blackthorn (Prunus spinosa) would normally have finished flowering by May, but the weather in the early part of 2013 was so cold, that spring was effectively delayed by several weeks.