This day is the luckiest one in the year especially if it falls on a Thursday. The herb,St Johns Wort is also called St Columba; if found accidentally and kept beneath the armpit, which is where the saint is said to have worn it, it will ward off evil.
Chant this as you pick it:
Arm pit package of Columba the kindly
Unsought by me, unlooked for
I shall not be carried away in my sleep
Neither shall I be pierced with iron
Better the reward of its virtues
Than a herd of white cattle.