Cut pieces of the pruned raspberry branches into 4-inch sections and dip them in a commercially available rooting powder.
Press the pieces into some sand, right side up and cover it loosely with plastic wrap.
Set the branches in filtered light and keep them moist until they root by misting the surface and watering the sand. You will now have several new raspberry plants to add to your patch.
Care for the new plants by watering them before they dry out, fertilizing them with organic fertilizer according to the package directions and planting them the following spring.