Take a cutting from the interior of the plant. Look for a branch that is growing straight up and cut off 6 inches. Make the cut just below a leaf node, so that the node is near the bottom of the cutting.
Place the cutting on top of a moist paper towel inside a plastic bag. Seal the bag to keep the cutting from drying.
Remove the blueberry cutting from the plastic bag and take off all but three of the leaves at the top of the cutting.
Mix equal parts of peat moss and perlite in a large planting pot and run water over it, stirring. Allow the mixture to drain completely and water it again, stirring. Pour the mixture into a smaller planting pot and allow it to drain completely. Poke a hole in the soil for the cutting.
Pour a small amount of root hormone into a small dish or saucer. Dip the cut end of the blueberry cutting into it so that at least the bottom 1 inch of it is covered.
Stick the cutting into the hole, making sure that at least two leaf nodes are buried under the soil. Use your hands to press the planting medium firmly around the cutting.
Set the heat mat in a sunny area of the house and turn it on to 70 degrees Fahrenheit. Place the pot on top of it. Keep the soil moist until the blueberry cutting roots. You can tell this has occurred when it has new growth.
Wait until the following spring to plant the blueberry plant outdoors.