Hailing from Mexico with ancient roots in the Aztec culture, the dahlia has a long and international history as a gardening favorite. Available in a dazzling number of sizes, forms and colors, dahlias are easily recognizable for their stiff petals that mound in a flat or rounded head at the top of a long, slender stalk. The popular bulb bloom is planted for late-summer color in spite of the necessity to dig the tubers after blooming for winter storage.
Dig tubers after the first frost, prior to November. Carefully use a spade to dig a wide hole around the entire planting area, to avoid cutting any newly formed tubers from this season. Use a garden fork to lift up the clump of soil containing the tubers.
Gently separate the tubers from the soil. Separate the clumps by type and label a marker to be stored with the various species over winter for easy identification. Cut any remaining foliage back to a few inches and spray the tubers with water. Leave them until completely dry.
Discard any tubers that appear to have disease or moldy spots, as these may spread their ailments to other tubers during storage.
Fill containers that will provide air circulation with peat moss. Place the clean, dry tubers upside down (with foliage stub facing down) in the peat moss.
Store the containers in a dry, cool place that remains a steady 40 to 55 degrees Fahrenheit throughout the winter. Check the tubers in mid-January for any shrinking or wrinkling of the skin. Ohio State University Extension expert Jack Kerrigan suggests that a small amount of water may be added to the peat moss if excessive shriveling has occurred. Take care not to soak the tubers or fungus could result.