Wait until frost kills the tops, or the foliage dies back on its own. The tubers keep developing for a while after the leaves fade. Dig before the ground freezes hard. In zone 8 and warmer, dahlias can usually stay in the ground. In zone 7, they can often overwinter in a well-drained spot under at least 4 inches of . Anywhere colder, dig them every fall.
Cut the stalks to about 4 to 6 inches right before you dig. Hollow stems left standing collect water that can rot the crown. Loosen the soil in a wide circle, about 18 inches out from the stalk, with a fork or spade. Then lift the clump from underneath instead of pulling on the stem. The neck where each tuber joins the crown snaps without much force, and a tuber broken off at the neck won't sprout. Avoid sharp tools near the tubers, since skin damage lets rot in.
Rinse off the soil, which can carry decay organisms, and let the clumps dry out of direct sun in an airy spot around 60 to 70°F for a day to a few days. Write the variety on each clump or tuber with a permanent marker. You can divide now or in spring. Eyes are often easier to see in fall, but undivided clumps tend to hold up better in storage. Each division needs at least one eye and a piece of crown.
Pack the tubers in a ventilated box or open bag, with coarse vermiculite, wood shavings, coir, peat moss, or sand around them. The packing should be barely moist, and the tubers shouldn't touch. Store them somewhere dark that stays above freezing, ideally about 35 to 45°F, like an unheated basement or an attached garage that doesn't freeze. Don't seal the containers. Trapped moisture builds up and invites rot.
Check the tubers about once a month. If they're shriveling, mist the packing lightly. Remove any soft or moldy tubers right away before the rot spreads to their neighbors. A few weeks before your last spring frost, move them somewhere slightly warmer, around 40 to 50°F, to wake the eyes. Divide any clumps you didn't split in fall, then plant about a week after your .
- Meadow VolePlants collapse with roots eaten; shallow surface runways and gnaw marks at stem bases near soil.
- Powdery MildewWhite powdery spots on leaves that spread into a floury coating — common when warm, dry days follow cool nights.
- Fruit CrackingTomatoes crack at the stem end or shoulder, cabbage heads split, and carrots split lengthwise — usually after heavy rain follows dry weather.
- Early BlightDark spots with concentric rings on lower leaves that yellow and drop, working up the plant.
- Septoria Leaf SpotNumerous small circular spots with dark borders on lower tomato leaves, which then yellow and drop, progressing upward.
- How do I store winter squash so it lasts through winter?Cure winter squash at 80–85°F for 10–14 days to harden the skin, then store at 50–60°F in a cool, dry location — not the refrigerator.
- What is a last frost date and how do I actually use it?Your last frost date is the average date of the final freezing night in spring — it's a probability, not a promise, and smart planting adds a buffer of 1–2 weeks beyond it for cold-sensitive crops.