Looked up the origin of blowing a dandelion and here is what I found:
Young girls commonly used dandelions in the 1800s for romantic and oracular purposes. It was believed that if you blew on a dandelion and all the seeds flew away, your loved one returned the feelings; if any seeds remained, they might have reservations or no feelings at all. Children would blow on these flowers while thinking hard about the objects of their affection. Eventually this tradition spread to encompass all wishing, romantic or otherwise.
