Lift dahlias, cannas and gladiolus in the week or two after the first frost that blackens their leaves. At NOAA’s Kansas City International station, a 32°F freeze typically first arrives between October 18 and October 29, so digging day lands in late October or the first half of November. Farther north the frost comes earlier and you dig earlier. In the southern part of the state you get a little more time. If the leaves say otherwise, trust the leaves over the calendar.
Do you have to dig them up in Missouri?
Yes. Missouri winters are too cold for these three to sit in the ground untouched, and the numbers leave little room for argument. The USDA Plant Hardiness Zone Map 2023 places the state in zones 5b to 7b. That system is built on a single variable, the average annual extreme minimum temperature. It describes the worst night of a typical winter and says nothing about how long the soil stays cold and wet. Plan on digging all three every fall.
Where the ground does not freeze deeply, a thick blanket of mulch can carry dahlias, cannas and gladiolus through winter. Missouri isn’t that place. NOAA’s 1991-2020 Climate Normals for Kansas City put the mean daily minimum of the coldest month at 19.5°F. That is not a record low or a freak cold snap. It is the ordinary nightly low of a typical winter month, well under freezing, night after night. Soil that endures weeks like that freezes, and a frozen dahlia tuber, which is mostly water, thaws into mush.
Where the line falls inside the state
The state runs from 5b at the cold end to 7b at the mild end, colder in the north and milder toward the south. Nothing inside that range comes with a data-backed promise that the ground stays soft all winter. Kansas City is the one place here with a measured figure attached, and the figure says lift. Southern Missouri is milder, which buys a later first frost and a slightly longer growing season, but not a pass on the whole ritual.
Cannas are the only one of the three worth a gamble. In the milder south, a sheltered spot, fast-draining soil and a deep layer of mulch will sometimes carry a clump through. The trouble is that wet clay, common across Missouri, kills more rhizomes than cold does. A canna sitting in cold, soggy ground for months is in worse shape than one in dry, frozen ground. Dahlias and gladiolus are poorer bets still, and a lost dahlia collection is a lot of money and effort to risk on a mild-winter hunch.
Hardy bulbs are the flip side. Tulips and daffodils spend the winter outdoors by design, and Which Spring Bulbs Survive Your Winter sorts out which ones do. The wider Spring Bulbs section covers the rest of that group. Dahlias, cannas and gladiolus belong to the tender crowd, the ones that only look like bulbs you can plant once and forget.
When to lift them
Wait for a frost that turns the foliage black, then dig within a week or two. At Kansas City International, NOAA’s 1991-2020 Climate Normals show the first 32°F freeze falling between October 18 and October 29, the band where the odds of that first freeze run from 30 to 70 percent. Add a week or two and lifting time runs from late October into the first half of November. Lift within a week or two of the first frost that blackens the foliage, which around Kansas City means late October into early or mid November.
Shift that window with your location. Colder northern Missouri sees its first freeze earlier, so digging moves earlier there too. Southern Missouri gets its frost later and can wait a bit longer. For a date closer to your own county, First and Last Frost Dates in Missouri has the local numbers. The blackened leaves are the real trigger, and a frost that arrives before or after the averages moves your digging day with it.
Why waiting matters
A tuber pulled in September or early October is like a green tomato: it looks fine and doesn’t keep. Until frost ends the season, the top growth keeps sending energy down into the roots, and the skins keep thickening. That skin is what holds moisture in and rot out over winter. Dig early and you get thin-skinned tubers that bruise easily, lose water fast and start to rot in storage. Dahlias add a second problem. Their hollow stems can carry moisture straight into the crown, and immature crowns are the first to go soft.
Waiting too long has a cost as well. Foliage that has been dead for weeks is hard to find, and tubers in cold, wet ground begin to rot where they sit. A hard freeze that reaches the soil can damage the tubers themselves. The one-to-two-week window is the sweet spot, roughly the time it takes for the plant to finish shutting down while the soil is still workable.
Lifting each one
Choose a dry day and let the soil be crumbly rather than sticky. For dahlias, cut the blackened stalks down to a short stub, push a garden fork in well away from the clump so the tubers aren’t speared, and pry the whole mass up. Cannas get the same treatment, with the stalks cut back and the rhizome clump loosened and lifted. Gladiolus are the most forgiving. The corms can come up once the foliage yellows, frost or no frost, so they can be dug on the same day as the others or a bit earlier. Cut the tops off, shake off loose soil and move everything somewhere sheltered.
The freshly emptied bed is a good place for tulips and daffodils, and Planting Spring Bulbs in Missouri covers when to get them in.
Storing them over winter
Storage comes down to three moves: cure, clean lightly, then keep everything cool, dark and slightly moist so it neither rots nor shrivels. Curing means letting the freshly dug pieces dry for a while in an airy, sheltered spot such as a garage, porch or shed, out of rain and sun and safely away from freezing. Turn dahlia clumps upside down at first so water drains out of the hollow stems. The surface should feel dry and the skin firm before anything gets packed.
Cleaning is minimal. Brush off loose soil with your hands or a soft brush and trim away broken or mushy sections. A hard scrub or a soak strips protective skin and invites rot. Storage should stay above freezing, out of light, and away from a furnace or water heater, because warmth wakes tubers up too soon and dries them out.
How the three differ
| Plant | What you’re storing | Packing | Moisture |
|---|---|---|---|
| Dahlias | Tuberous roots with a crown | Boxes or crates, wrapped or layered in peat, vermiculite or wood shavings | Slightly moist, never wet |
| Cannas | Fleshy rhizomes | Boxes with damp peat or sawdust, in large pieces | Slightly moist, a bit more forgiving |
| Gladiolus | Corms | Mesh bags or paper, in a single airy layer | Dry, with good air circulation |
Dahlia tubers are the thirstiest of the three for humidity, which is why they get packed in a lightly damp medium. Left bare in a dry basement, they wrinkle. Cannas want much the same, and keeping the rhizomes in big chunks helps, since small pieces dry out faster. Gladiolus break the pattern. Their corms want dry, moving air. Break off the old shriveled corm at the base, keep the plump new one, and hang the bags somewhere ventilated. Damp packing gives them mold.
Whatever the plant, one habit saves more collections than any storage trick. Check every box and bag once a month from November until it’s time to plant. Pull out anything soft, dark or moldy, and cut back to clean tissue if the damage is small. If tubers look wrinkled, add a little dampness to the packing material. If they’ve started sprouting, move them somewhere cooler.
What goes wrong
Problems in storage
Rot is the big one. It shows up as soft, dark, mushy spots, sometimes with a sour smell or gray fuzz. It starts with tubers that were dug too early, packed before they dried, or stored in damp, still air. Cure fully, remove damaged pieces before packing, and give the boxes some ventilation. Rot spreads to neighbors, so pulling a bad piece early saves the rest.
Shriveling is the opposite failure. Tubers turn wrinkled, rubbery and light, and the eyes on a dahlia crown may never wake up. The cause is storage that is too warm or too dry, or no packing medium at all. A slightly damp medium and a cool, dark spot prevent it, and the monthly check catches it before it’s fatal. A tuber that has gone wrinkly but is still firm at its core can often be rescued with a little moisture.
Problems in timing and placement
Lifting too early gives thin-skinned tubers that look fine in October and fall apart by January. The fix is patience, which means waiting for the frost that blackens the foliage rather than tidying the garden on a warm weekend in early fall. Lifting too late has its own price: cold, saturated soil and the risk of a hard freeze reaching the roots.
The last mistake is leaving plants outdoors one zone too far north. Catalogs and plant tags often call these perennial in warmer regions, but Missouri runs 5b to 7b, and Kansas City’s coldest month averages a nightly low of 19.5°F. A tag written for a milder climate doesn’t describe your soil. If you want to test hardiness, leave one spare clump in the ground under heavy mulch and lift the rest. If it comes back in spring, you’ve learned something about that one spot, and you still have the rest of the collection in the basement.
Common questions
Do I have to wait for frost to dig gladiolus?
No. Gladiolus corms can come up once the foliage yellows, and many gardeners dig them before the first frost. Waiting is fine too, as long as the ground isn’t waterlogged. Dahlias and cannas are the ones that benefit most from waiting for the blackening frost, because their tubers and rhizomes keep maturing until top growth dies.
Should I wash dahlia tubers before storing them?
Brush off loose soil and leave it there. Some growers rinse and then dry thoroughly, but skipping water lowers the risk of rot, and thin, wet-scrubbed skin is what invites it. Whichever way you clean, the tubers should be completely dry on the surface before they go into boxes.
Can I leave cannas in the ground in southern Missouri?
Sometimes, but it’s a gamble. Southern Missouri is milder than Kansas City, where the coldest month averages a nightly low of 19.5°F (NOAA, 1991-2020), yet no figure here promises unfrozen soil. A sheltered spot with sharp drainage and deep mulch gives cannas their best chance. Wet clay is the biggest threat. The Missouri guides cover timing across the rest of the state, but for cannas you’d be relying on mulch and luck.
When do I plant them back out?
After the last spring frost, once the soil has warmed. Dahlias and cannas both blacken at the first touch of frost, so a late cold snap after they’ve sprouted means covering them overnight. If tubers sprouted in the box during late winter, pot them up indoors and keep them in a bright spot until the weather settles.