The theory of over wintering dahlias sounds simple; dig them up and store them in a frost-free place until late spring, when the ground is warm enough to plant them out again. But unless you do this systematically, you'll find that storing your dahlias is a waste of time. Shrunken or moldy tubers aren't going to perform even if you bother to replant them, and even if you manage to get your tubers through the winter in good shape, if you haven't tagged them properly, it's going to be impossible to plant the display of dahlias you were anticipating.
The first step in preparing your dahlias to survive the winter is to gather the information about the varieties of dahlias you grew this year so you can tag them. Believe me, a dahlia tuber gives no clue as to what kind of dahlia it will produce! If you haven't tagged them, you'll have no clue what's what in the spring. To make tagging dahlias less of a chore, several of us dahlia fans have gotten together and created a "Dahlia Log" that lists a description of each type of dahlia we grow.
The Dahlia log is organized by the categories of dahlia classification. The American Dahlia Society recognizes 18 classifications of form. We use a simplified system based on the dahlia varieties we have which might work well for you, too:
A) Single: one row of petals (two if duplex) encircle a central disk of stamens.
B) Anemone: Flat ray petals surround tightly packed, tubular disk petals.
C) Collarette: A collar of small petals lie between the ray petals; have a yellow disk.
D) Peony: 2 to 4 rows of flat ray petals surround a disk of twisted petaloids.
E) Cactus and Semi-Cactus: Fully double flowers, pointed ray petals.
F) Ball: Spherical flowers have blunt, quilled petals, set in a spiral pattern.
G) Waterlily: Fully double and symmetrical blooms with a side view that appears to be flat or saucer shaped.
H) Decorative (includes Dinner Plates): Double flowers with no central disk. Can be symmetrical or irregular.
