Answer: Dahlias, like begonias, aren't hardy where the ground freezes, so you'll have to "lift" the tuber from the container. Plants in containers, even if they're hardy, need extra winter protection, since they have less insulating soil surrounding them. Try this next fall to be sure your dahlia will regrow. Wait until frost kills the tops, and cut the tops back to 4" above the crown. Gently lift the tubers from the container with a garden fork, or dump the container over to release them. Shake of excess soil and allow them to dry a bit, then store them in dry sawdust or peatmoss in a cool, dry place. If you don't have a basement, store them in your coolest closet or cabinet. In the spring, when little buds begin to show at the neck of each tuber, divide, leaving one bud per tuber, and replant them in moistend soil.
Begonias prefer relatively humid climates and moist shade. Maybe they were too dry to store well. If you want to try again, keep their container in filtered shade, and place it in a tray of water filled with small stones. Don't let the container touch the water, though - just the evaporation from the tray may be enough to adequately humidify the plant. Also, keep the soil in the pot mulched to preserve moisture. Best of luck!
Q&A Library Searching Tips