Dahlias, cannas and gladiolus come out of Rhode Island soil after the first frost blackens their leaves, not before. In Providence, NOAA’s 1991-2020 normals put the first 32°F freeze between October 24 and November 3, so the digging happens in the days that follow. Gardens inland and away from the water usually freeze one to two weeks sooner. Below you’ll find why the ground can’t keep these plants, how to time the dig, and how to get the tubers through to spring.
Do you have to dig them up in Rhode Island?
Yes, with very few exceptions. The USDA Plant Hardiness Zone Map (2023 edition) places Rhode Island in zones 6a to 7b. At the Providence reference station, NOAA’s 1991-2020 climate normals give a mean daily minimum of 22.1°F for the coldest month. That is an average night, not a record. Half the nights in that month, give or take, are colder, and the soil follows the air down.
Dahlias come from the highlands of Mexico, cannas from the tropical Americas, and gladiolus from southern Africa. None of them evolved with frozen ground. Their storage organs (tuberous roots, rhizomes and corms) are mostly water, and once ice forms inside them the cells burst. What comes out of the soil in April is a mush that smells like a bad potato.
The USDA zone system rests on a single variable, the average annual extreme minimum temperature. It says nothing about how wet your soil is, and wet is the other half of the problem. A tuber sitting in cold, saturated New England clay can rot long before the temperature gets lethal. Mulch doesn’t fix this. A thick blanket slows the freeze, but at 22.1°F nights it only delays the inevitable, and it holds moisture right against the tubers.
The map’s range of 6a to 7b means conditions differ across the state. The milder pockets sit along the coast and islands, and the colder ones in the northwest hills. At the mild end, some gardeners get cannas through a gentle winter under heavy mulch. A plant that survives three winters and dies in the fourth was never really hardy, and the loss usually comes in the year you stopped paying attention.
Plan to lift all three every fall, once frost has blackened the foliage, which around Providence means the days after October 24 to November 3. If you want to experiment with leaving one in the ground, make it a spare, never your best.
True hardy bulbs follow different rules. Daffodils and most tulips are happy to stay put, and you can sort out which ones in Which Spring Bulbs Survive Your Winter. The broader Spring Bulbs section covers the planting side of that group.
When to lift them
Let the frost do the first step
The signal is a frost that turns dahlia and canna foliage black and limp. Don’t dig on a calendar date. The frost is a cue that the plant has stopped growing and the tubers are starting to harden off, and the tops need a short while to finish feeding the roots before you cut them.
For the Providence airport station, the 1991-2020 normals from NOAA’s National Centers for Environmental Information put the first fall freeze at 32°F between October 24 and November 3. That window is the 30 to 70 percent probability band, meaning in a typical year the first freeze lands somewhere inside it. Lifting then falls in the days after, within about a week or two of the frost that blackens the leaves. Treat it as the reference-city figure, not a statewide promise.
Your garden may not match the airport. Suburban and rural sites usually see the first fall frost earlier than a city weather station, often by one to two weeks, and more at higher elevation. In practice a garden in the northwest part of the state may be blackened and ready to dig before Providence has had a single freeze, while a spot right on the water may wait past the end of that window. Check the frost data for your own county, and the First and Last Frost Dates in Rhode Island page is a good place to start.
Why lifting early backfires
The temptation is to dig in mid-October “to be safe.” Resist it. Tubers lifted while the plant is still green and actively growing have thin skins and haven’t finished maturing. They lose water fast in storage, shrivel, and open a door for fungus. The ones that don’t shrivel often rot from the neck, where the stem was cut while still full of sap.
Waiting for the frost gives the tuber a chance to seal itself. The opposite mistake matters too. If a forecast calls for a hard freeze that will lock up the soil, don’t wait around for a tidy sequence. A light frost that kills the foliage is the cue to dig. A deep freeze that gets into the ground is the cue to have already dug.
Gladiolus run a little differently. Corms are usually dug when the leaves start to yellow, which can come before or around the first frost. If a frost hits first, the corms are fine for the short run, so lift them in the same few days as the others.
The decision to write on the calendar: once frost blackens the foliage, dig within about a week or two, which in the Providence area follows the October 24 to November 3 window. Pick a dry day when the soil isn’t soggy, because mud clings to tubers and keeps them wet.
Cut the stalks back to a short stub and dig a wide circle around the clump, well outside where you think the tubers reach. Dahlia necks snap easily, and a broken neck means that tuber won’t sprout. Lever the clump up with a garden fork, never by pulling the stem.
Storing them over winter
Cure and clean
Once the clumps are out, shake off the loose dirt and leave them somewhere sheltered and airy, out of rain and direct sun, so the surface can dry. Don’t wash them hard. A light brush is enough, and a hose soaks the tubers and encourages rot. Cannas and dahlias need only until the skins feel dry to the touch. Gladiolus corms take longer, because they are meant to go into storage fully dry, with the old shriveled corm and any loose husks pulled away.
Look each piece over as you clean. Anything soft, black or oozing goes in the trash, not the compost pile. A firm tuber with one bruise can be trimmed back to clean tissue and dusted dry. Label the clumps by variety as you go (a strip of masking tape and a pencil work), because in March every tuber looks identical.
Three plants, three different needs
Keep the place cool, dark and above freezing: an unheated basement, a cellar room, or an insulated garage that holds above freezing all winter. A spot that sits at the temperature of your living room dries them out. One that dips to freezing kills them. The three plants want the same place but slightly different packing.
| Plant | What you store | Packing | Moisture |
|---|---|---|---|
| Dahlia | Tuberous root clumps | Boxes or crates with lightly damp, loose material such as wood shavings, peat or vermiculite | Slightly moist, never wet; shrivels if dry, rots if damp |
| Canna | Rhizomes with a short stub of stem | Crates or paper bags with lightly damp packing | Slightly moist; the rhizomes are thick and dry out slowly but suffer if bone dry |
| Gladiolus | Corms, cleaned and dry | Mesh bags, paper bags or open trays | Dry, with good air movement |
The difference comes down to the structure. Dahlia tubers and canna rhizomes are fleshy and lose moisture through the skin, so they want a touch of humidity around them. Gladiolus corms are compact and tunic-covered, and they store best dry. Putting them in damp sawdust is the surest way to get a bag of mold.
Leave one layer of packing material between pieces so they don’t touch, and use crates or cardboard that can breathe. Plastic bags look convenient, but they trap condensation and ruin batches by February. If you use them, leave them open.
The monthly check
Storage isn’t a set-and-forget job. Check the tubers once a month, from the day they go in until the last spring frost has passed. Pick up a few, give them a squeeze, and look for soft spots, mold or wrinkling. If a tuber is going soft, pull it out before it spreads. If packing is dusty and the tubers look wrinkled, mist the material lightly. If things feel wet or musty, open the container and let it air for a day.
That ten-minute habit saves more tubers than any storage trick. After the last frost, the plants can go back outside. The First and Last Frost Dates in Rhode Island page covers the spring side of that calendar.
What goes wrong
Rot is the most common failure, and it announces itself. Tubers turn soft and dark, sometimes with a gray fuzz, and the smell is sour and earthy. It comes from packing that was too wet, storage that was too warm and stuffy, or tubers lifted before they had finished maturing. Prevention is dry hands and dry weather at lifting, a full surface cure, and open airflow in the container.
Shriveling is the opposite problem. The tuber looks like a raisin, with deep wrinkles and a rubbery feel. It means the air was too dry or the packing was missing entirely. Mild wrinkling can be reversed with a light misting of the packing material, but a tuber that has gone hard and hollow is finished.
Lifting too early produces both at once. Immature tubers with thin skins dry out fast, and the cut stems stay open and weep. That’s why the wait for blackened foliage matters, and why a frost that comes before your schedule is a gift rather than a nuisance.
Then there’s the zone gamble. Leaving tubers in the ground one zone too far north is the mistake that feels harmless until spring. Gardeners at a milder coastal spot in Rhode Island may see a canna or two survive and decide to skip digging, then move that habit to a colder inland yard. In the state’s colder areas the soil freezes harder and for longer, and nothing comes up. If you are tempted, cut the risk to a single spare clump, never the whole bed.
One last note for gardeners who also plant hardy bulbs: those follow a very different calendar. The Planting Spring Bulbs in Rhode Island page covers when tulips, daffodils and the rest go in. For the full range of local advice, see the Rhode Island guides.
Common questions
Can I leave cannas in the ground in Rhode Island?
Not reliably. With the USDA zone range running from 6a to 7b and the Providence coldest-month mean minimum at 22.1°F, a canna left in the ground is a gamble. A few survive in sheltered, mild coastal spots under heavy mulch, but a harder winter will take them. Lift them and store the rhizomes if you want to keep them.
Do I have to wait for frost before digging dahlias?
Waiting for frost to blacken the foliage is the best signal that the tubers have matured. In Providence the first 32°F freeze normally falls between October 24 and November 3, earlier in colder, higher or more rural gardens. Digging a week or two after that frost is the usual window. The exception is a forecast hard freeze that will freeze the soil, in which case dig first.
Do gladiolus corms get dug at the same time?
Mostly, yes, though they follow the foliage more than the frost. When the leaves yellow and fade, the corms are ready, and that can happen before the first frost. Dig them in the same stretch as the dahlias and cannas, cure them dry and store them in mesh or paper bags, not in damp packing.
Where is the best place to store them?
Anywhere cool, dark and above freezing: a cellar room, an unheated basement or an insulated garage. The spot should stay steady, away from furnaces and cold exterior walls. Keep a thermometer there for a few days before committing, because a corner that feels fine in November can freeze in the depths of the coldest month.