Apollo teased Eros (Cupid) about shooting his bow and arrows. Cupid in his anger came up with a mischievous idea. He flew up a mountain with two arrows. One of gold and one of lead. The gold one would make the victim fall desperately in love with whomever they saw next. The lead one would freeze a heart, and the person could/would not love.
Eros spied the lovely nymph Daphe, and shot her with the lead arrow. She ran to her father, a minor river god. She begged him to allow her to remain chaste and unmarried. He loved her very much but was deeply saddened by this. He granted her wish though.
A small bit of time later Eros saw Apollo walking nearby and so he struck him with the golden arrow, causing the god to fall madly in love with poor Daphne.
He began to chase her but since she had been with Artemis's hunters and was a nymph (not human) she was able to just barely evade him.
She cried out to her father for assistance, and he granted her her wish to remain alone. He turned her into a Laurel tree.
Apollo cried and kissed the bark repeatedly but the lovely nymph was already gone. He took down some of the branches and wore a Laurel crown so he could always have his 'love' with him. And then it became his sacred tree.
It later became a important Grecian symbol, often of power, knowledge, and/or Apollo's favor.
