Myrobalan plum

The flowers of the Myrobalan Plum (Prunus cerasifera) are often mistaken for Blackthorn (Prunus spinosa), but it flowers about a month earlier.  The flowers are a purer white than Blackthorn and they appear on the green twigs just as the leaves are opening.  Blackthorn twigs are darker - purply black - and the side shoots often end in sharp spines.  Another sure way to tell Blackthorn from Myrobalan (also called Cherry Plum) is to taste the fruits in autumn.  Cherry Plums are sweet but the Sloes on Blackthorn are sour enough to make your face crumple.