Loosen the soil on either side of the rutabaga plants or rows with a handheld garden fork. Avoid digging in the center of the row because the fork can pierce and ruin the mature roots.
Grasp the plant stem near the base, and lift the roots out of the loosened soil. Slide a trowel under the roots, if necessary, to dislodge them from harder soil.
Cut off the stem to within 1 inch of the root with a sharp knife. Wipe the soil off the outside of the root with a moistened cloth.
Place the rutabagas in a slatted box or a cardboard box with ventilation holes in the sides. Keep them in a cool location that is between 32 and 35 degrees Fahrenheit for up to four months.