From Ground: First, water the dog tail deeply to loosen the soil. Using a shovel or spade, dig a circle around the plant that's wide enough to include all its roots. Carefully slide the shovel underneath the root ball to lift the dog tail out of the ground with as much of the root system intact as possible.
From Pot: Water the soil in the pot prior to removing the dog tail to make the removal easier. Tip the pot to the side and gently tap the base to loosen the dog tail from the pot. Grasp the base of the dog tail and ease it out, being careful not to tug on the stems.
From Seedling Tray: Water the seedlings before transplanting to ensure the soil is moist. Use a trowel or your fingers to gently pry the dog tail seedling out of the tray, taking care to keep the root ball and surrounding soil as undisturbed as possible.