Dahlias are breathtaking plants that bloom large flowers from summer until fall. After blooming, the plants continue to store nutrients in their underground root structures called tubers, which also have all the components they need in order to grow new dahlia plants the next year. However, since tubers are planted just below the surface of the soil, they generally cannot tolerate the winter outdoors, so you must dig them up in late fall for winter storage.
Allow the dahlia tubers to dry. Turn them upside down so the stems can drain and the soil around the tubers can dry. This should only take a few hours and will make handling them much easier, but still, be careful around the shoulder area of the tubers since they are narrow and fragile.
Remove the rest of the soil when the tubers are dry. It's important to get all the soil off as it may have a fungus or disease that will harm your tubers in storage. Wash them off with water, if necessary. Just don't get any water into the stem. Allow the tubers to dry for about 24 hours before storing.
Put about 3 inches of peat moss in a cardboard box. You can also use a bushel basket, wooden flat or similar. Sit the tubers on top, with the stems facing up. Then, add more peat moss until just a little bit of the stems are sticking out.
Store the tubers until spring in an area that is between 40 to 55 degrees F and is dry. The attic, attached garage, cupboard or crawl space may be an ideal location in your home.