How to Dig, Wash and Store Dahlia Tubers in Zone 3 (How We Do It on Our Farm)

Quick answer

In zone 3, dahlia tubers have to come out of the ground every fall. Dig them once they've had at least 120 days in the ground and before the soil freezes. Then clean them up, trim off the small roots, label every tuber and pack them in tubs layered with vermiculite or wood chips. We store ours in our CoolBot cooler at about 5°C all winter, with two temperature monitors so we always know it's safe.

Your dahlias are out of the ground? Now what?

That was the start of our most saved Reel this fall, and your questions in the comments are what this post answers. Here's exactly how we dig, wash and store our dahlia tubers on our zone 3 flower farm at Charlie Lake, BC, with our real dates and the setup that keeps them safe all winter.

Do I have to dig up my dahlias in zone 3?

Yes. In zone 3 our ground freezes far too deep for dahlia tubers to make it through the winter. Freezing ruins tubers, so if you want your dahlias back next summer, they have to come out every fall.

The good news is that once they're tucked in for the winter, every tuber you save is a plant for next season.

When should I dig dahlia tubers?

Dig once your dahlias have had at least 120 days in the ground, and always before the soil freezes.

A lot of growers wait for a killing frost before they dig. When I started, my reading said frost wasn't required, and the research agrees. Penn State Extension says dahlias need at least 120 days in the ground to make mature tubers for storage, and that waiting for the first frost is unnecessary. What matters is time in the ground.

Here's what that looked like for us this year:

Our average last frost is May 15 and our first fall frost is around September 15, so in zone 3 every day in the ground counts. That's why our goal next year is to plant earlier, not dig later.

A few hard limits we follow:

• Dig before the soil freezes. Frozen tubers won't keep.
• If a hard cold snap is in the forecast, dig right away. Digging in the cold is worse than digging when it's warmer. 
• A run of cold, heavy rain is a reason to dig sooner, because waterlogged soil raises the risk of rot.

Before we dig, we cut the stems down and then wait 3 to 5 days. The American Dahlia Society suggests the same thing: cut the tops back to about 6 inches, 3 to 5 days before you dig, so the eyes are easier to see. Don't leave the cut stalks sitting much longer than that, because rot can start in the crown.

Do I need to wait for frost to dig my dahlias?

No. You do not need to wait for a frost to dig your dahlias. This is one of the most common pieces of advice out there, and it's one of the "buts" that trips new growers up. Time in the ground is what matures the tubers. We dug ours on September 30 this year, once they'd had 123 days in the ground.

What do you use to dig dahlia tubers?

We dig ours with a potato pitchfork. It's nice and strong, which is exactly what you want for lifting dahlia clumps out of the ground.

How do I wash and clean dahlia tubers?

Once the clumps are out of the ground, we wash the soil off. This fall we washed about 800 dahlia tubers. Clean tubers make it much easier to see what you've got and find the eyes when it's time to divide.

Then we clean each one up. We cut off all the small tubers and all the small, thin roots, so we're left with a tidy tuber that's ready to store.

Do I divide dahlia tubers in the fall or the spring?

Growers do both. We divide ours in the fall, in our warm shop over a couple of days, before anything goes into storage.

How do I label dahlia tubers so I don't lose track?

This one matters more than you'd think. Once they're washed and divided, it's easy to lose track of which tuber is which.

We label every tuber two ways. First, we tie a ribbon on it with the variety name. Second, we write the name right on the tuber with a garden marker. If a ribbon slips off over the winter, the name is still there.

How do I pack dahlia tubers for winter storage?

We store ours in large Rubbermaid tubs and layer them like a lasagna.

Here's how we do it:

1. Clean up each tuber and cut off the small tubers and small roots.
2. Label it with a ribbon and write the variety name on it with a garden marker.
3. Add a layer of vermiculite or wood chips to the bottom of the tub.
4. Add a layer of tubers, then cover them with more vermiculite or wood chips.
5. Keep layering until the tub is full, then put the lid on.

Then we use the tractor to move the full tubs into our cooler for the winter, where they stay tucked in until spring.

Where do I store dahlia tubers over winter, and how cold should it be?

We keep ours at about 5°C all winter, in our CoolBot cooler.

We built our CoolBot walk-in cooler in 2025 to keep our cut flowers fresh in summer. It's an insulated shed with foam insulation, cooled by a standard window air conditioner hooked up to a CoolBot controller, which lets the air conditioner cool the room far lower than it normally would.

In the winter, we flip the job around. In zone 3 the danger is the cold. So we use an Inkbird temperature controller that runs a small space heater, and it holds the cooler at about 5°C. That's cool enough to keep the tubers resting and warm enough to keep them from freezing.

How do I keep an eye on stored tubers?

We use at least two different temperature monitors in the cooler, so we're never relying on just one. One of them sends an alert to our phone if the temperature dips below a set point, so we can check on our tubers from wherever we are.

The honest part

Digging, washing, dividing, labelling, packing and moving tubs with the tractor. It's a lot of work for a flower you won't see again until next summer.

But every tuber we tuck in this fall is a dahlia next season.

Questions growers ask

Do I have to wait for frost before digging dahlias?

No. What matters is time in the ground. We aim for at least 120 days, and we always dig before the soil freezes.

What do you dig dahlias with?

A strong potato pitchfork.

What do you store dahlia tubers in?

Large Rubbermaid tubs with lids, layered with vermiculite or wood chips like a lasagna.

What temperature do you store dahlia tubers at?

About 5°C. Our cooler is held there all winter with an Inkbird controller and a small space heater.

How do you keep dahlia names straight?

Two labels on every tuber: a ribbon with the variety name, and the name written right on the tuber with a garden marker.

Should I divide dahlias in fall or spring?

Growers do both. We divide ours in the fall, before they go into storage.

Want dahlias next summer?

Our dahlia tubers are dug, divided and stored right here on our zone 3 farm. They're available online and ship within Canada starting May 1, weather permitting.

Planning your dahlias for next season? Stemwise is a cut flower planning app that works out what to start, when to start it and when everything will bloom for your zone and your frost dates. Stemwise is coming soon. You can start today with a free plan for your first bed at mystemwise.com.

Find our dahlia bloom dates and every other guide in our Zone 3 Growing Guide.

About Cory
Cory Franklin is a retired RN who had never grown a flower before she started Franklin & Co. Flower Farm, a zone 3 u-pick flower farm in Charlie Lake, BC. She is also the founder of Stemwise, a cut flower planning app. She shares what happens in her flower field, real dates and all, so you can grow with less guessing.

More from our flower field

• We Built a CoolBot Flower Cooler
• Why Season Extension Is Essential for Flower Farming in Zone 3
• When to Start Cut Flower Seeds in Zone 3

So tell me... do you wash your tubers, or store them dirty?

– Cory