After receiving your dahlia tuber in the mail, dig a hole where you want the flowers to bloom in your garden. It should be big enough to place the whole tuber into and be completely covered by dirt. Before planting your tuber, you need to find where the head is. Find where the stalk was last year. When placing it in the ground, make sure the stalk is pointing up. After planting, your tuber should be flowering in about 4 weeks. Because the wind and rain can be tough on your flowers, it's a good idea to use a stake so that the flower stems don't bend or break.