Overwintering Dahlias takes a little time and effort but the reward is well worth it.
12 SIMPLE STEPS
Label your plants at the base with a heavy duty tag and string or wire. Include the name, color and height if known.
Cut the plants down to about 2.5’ from the ground. Carefully loosen the soil around the plant with a gardener’s fork. Teasing the dirt loose from around the plant’s roots (tubers). When you’ve carefully loosened the soil enough, gently release the plant from the ground in one whole piece. Use the 2.5’ stalk if necessary, to help pull the plant out. If your gardening tools pierced or sliced a tuber, they won’t be a viable plant to overwinter.
Trim off the bulk of that green material- leaving a 6” nub. Remember to keep the plant label attached to the tuber. You may need to reattch it with string or another wire.
Bring the tubers into a basement or to a cool, dry space and allow the stems and tubers to dry out for about 2 weeks. Any dirt that was caked on when removed from the ground, will easily sluff off with a dust broom once dry.
Dust off any dirt and carefully separate any mushy tubers from the bunch. These will contaminate the tubers and cause the good parts to rot if not removed.
Purchase a large block of peat moss and prep your planting area with dry cardboard boxes.
Fill the cardboard box with a layer of peat moss and carefully place the labeled tubers flat- leaving room between each grouping.
Cover the 1st layer with a little more peat moss, then a row of newspaper, then peat moss and tubers and repeat. Each box shouldn’t have more than 3 layers of tubers.
Around the month of February, you can plant them in grow pots with slightly damp peat moss (moistened with a spray bottle) making sure the stem nub is exposed and the plant is labeled with a tag.
Place grow pots in a warm sinny spot in your house and don’t water until you see signs of life (green leaf shoots).
In early June when the weather is warm, plant them in the ground so that the base of the plant (the eye) is even with the top of the soil.
Water according to the weather.