The Common Hawthorn is a shrub or small tree 5–14 m tall, with a dense crown. The bark is dull brown with vertical orange cracks. The younger stems bear sharp thorns, 1 to 1.5 cm long. The leaves are 2–4 cm long, obovate and deeply lobed, sometimes almost to the midrib, with the lobes spreading at a wide angle. The upper surface is dark green above and paler underneath.
The hawthorn, once known simply as ‘May’, is naturally enough the tree most associated with this month in many parts of the British Isles. When we read of medieval knights and ladies riding out ‘a-maying’ on the first morning of May, this refers to the flowering hawthorn boughs they gathered to decorate the halls rather than the month itself. For on this day, according to the Old Style calendar that was in use until the 18th century, the woods and hedges were alight with its glistening white blossoms.
This and similar customs to welcome in the summer flourished in rural places until quite recently. In some villages, mayers would leave a hawthorn branch at every house, singing traditional songs as they went. The seventeenth-century English poet Robert Herrick wrote:
There's not a budding boy or girl this day,
But is got up and gone to bring in May;
A deal of youth ere this is come
Back, with whitethorn laden home.
Source: Wikipedia