Saving Summer Bulbs – Cannas and Dahlias

Nobody talks much about it, but the truth is the damn things tend to multiply.

canna tropicana in flower

While this is going on above ground, extension is transpiring underneath.

In the space of a single summer, one wizened little dahlia tuber can become a clutch of potatolike lumps the size of a basketball and the cannas are even worse – or better, if you’ve got a spot that could use a mass of something. Just because they got overused in the days of carpet bedding shouldn’t consign using cannas as hedging to the dustbin of horticultural history.

canna tropicana + millet purple majesty

A section of the side yard hedge (as seen from the driveway) at the Hudson Valley house. The canna is 'Tropicana;' the neat black grass is millet 'Purple Majesty.'

This is by way of saying that – assuming you’ve got room in the cellar or garage –  too much of a good thing may be just enough. And of course a bit more of an expensive thing is its own kind of gratification.

To Save Cannas and Dahlias Over Winter In Cold Climates.


1. Wait for the frost to kill down the tops. Expert opinion is divided on the necessity for this, but in my experience the unpleasant shock does seem to encourage the rhizome to think good thoughts about dormancy.

2. Choose a dry day to dig them up. Do so. Allow the dirt to fall off, and let the surface dry if it’s wet. (Some people wash and dry them, then dust with fungicide. I don’t.)

3. Clip off the dead stems, leaving a stub about  2 inches tall; there can be incipient buds underneath. Cut off any chunks of rhizome that are obviously diseased, but other than that leave them alone.

Again, the experts are divided. Some say this is the time to cut off dead sections and divide the good parts, but by me the fewer wounds there are, the fewer chances there are for needed moisture to leave or unneeded rot to enter.

4. Line a thick black plastic garbage bag or plastic storage box with a layer of light, air-holding insulation – peat moss, coir, pine needles, or packing peanuts – just deep enough to cradle the rhizomes and cover them thinly. Nestle the rhizomes into it, right side up and not touching.

5. Store in a cool but not cold place, 45 -50 degrees is ideal, five more degrees either way won’t make much difference. Leave the top partially open or partially cover, as the case may be, so moisture is held in but not trapped.

Check every month or so, opening the bag/cover a bit more if the rhizomes look sweaty, sprinkling very lightly with water if they appear to be drying out. Some of the buds may show signs of growth. No worries; they usually proceed very slowly; just try to avoid breaking them off.


Same routine as the cannas, except:

1. Cut the dead stems off short, about ½ inch long. The incipient buds are nestled at the neck of each tuber where it meets the stem and any extra stem will simply rot if it doesn’t dry out.

2.  If the clump is at all sizable, there will be dirt trapped between the tubers. I ( or as often as not Kristi) turn the clumps upside down and let them dry off  before removing any rotten tubers and proceeding toward storage.

Sometimes the clumps fall apart into smaller clumps or an individual tuber may separate from its fellows. No problem. Unless you count

Labeling, the curse of dahlia storers everywhere.

Over the years I have tried:

1. Putting each variety in a labeled brown paper bag before nestling in the insulation. Works pretty well if the bags don’t disintegrate.

2. Writing with sharpie right on one or more of the tubers in each clump. Works fine if the writing doesn’t fade and the tubers stay clumped.

3. Writing on a plant label and pushing the point between a couple of close tubers or stabbing it into a stem. Again, works fine “if “– in this case if the label doesn’t fall out into the general mass.

4. Writing on a strip of flat plastic plant tape and tying it to one of the stems. This is Kristi’s preferred method and therefore the one in current use. Works pretty well, in part because at this point we have so many tubers each variety can have a private section of the storage box.

bengal tiger and lilies

The good thing about planting something pink close by is that it brings out the pink leaf edge as well as the pink stem. This is canna x 'Pretoria,' aka 'Bengal Tiger.'

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  • Tatiana Said,

    I know nothing, but nothing of saving tubers, but wouldn’t a bunch of small/medium cardboard boxes work? Like the kind we get at work for paper? We recycle hundreds of them a week, and tons of people take them home for filing/moving/storage. One box per variety would keep them together regardless of how they fall apart, right?

    Hi Tatiana –
    Thanks for the reminder! Separate containers do solve the problem, and boxes are sturdier than bags, hence less likely to fall apart from dampness absorbed from their contents. Only downside to multiple boxes is that if you have a lot of tubers they take up a lot of space and need a lot of packing material. Fortunately, it sounds as though you and your colleagues at work might have access to tons of shredded paper, too. I’ve never tried it with bulbs but it ought to be fine as long as it doesn’t get wet.

  • Paul Said,

    Thanks for the ultra-timely tips, especially on the spectre of dahlia labelling. (After this year’s cavalcade of color chaos, my solemn vow is to avoid such surprises next year through fastidious labelling.)
    I like the plastic tape idea (#4) – I’d been cutting up used mini-blinds and wiring them to the stems but this sounds much easier & faster. Can’t wait to give it a try this weekend!
    Another big advantage of “permanent” labels is that you can leave them attached when you plant the tubers out the next year, saving loads of effort at harvest time. Even if the stems have rotted away by then, the labels stay in the right place, ready to reattach during the Great Fall Dig-Up.

  • This advice is so timely, as digging out dahlias is part of the “in & out” season in the Périgord: dig out dahlias, plant tulips in their places. It gives a sort of rotation of future color. There are still a few dahlia clumps to lift, but I now know to wait for a drier week. Storage in paper bags has worked here, but this time ’round will add some packing peanuts – and put the bags in long flat boxes, hoping for the best. Our “temperate zone” has in recent winters become a danger zone for some bulbs and plants not protected or lifted. Now to plan where to put them in the spring!

    Marolyn, what a great concept! I love the idea of switching off tulips and dahlias year after year. Somehow I’d imagined the Périgord warm enough to allow you to keep (well-mulched) dahlias in the ground, but it sounds as though I’ll have to revise that estimation. Packing peanuts and long flat boxes should be great for storage, but if plain old paper bags have always worked in the past, I can’t see any reason to change your routine now.

  • Lynn Dickson Said,

    Yes, those cannas certainly do multiply. I’m gardening in a Mediterranean climate in sunny Queensland, Australia (very wet at the moment) and have a wonderful display of cannas in a very damp patch. However, I’m able to keep them curtailed by regularly running the ride-on mower around their border. Goodness knows what’s happening under the ground though – perhaps in years to come we’ll find cannas 100 metres away with a giant underground rhizome system. I cut them down hard every winter and don’t need to lift and store. Only gets to about -4 C here in winter and then only for a few days.

  • Greg Martin Said,

    One nice thing about canna tubers multiplying is that they’re edible! Kind of like growing potatoes but without the disease problems and much prettier. And just like potatoes you dig them up and bring them in to store, and eat. It’s the young white (on some varieties other colors) tubers that you cook, the older tubers being too fiberous. I bake them until soft and tender and then enjoy. Not sure if all cultivars are as good as the next, so try several.

    Welcome, Greg
    and thanks so much for the tip/reminder. Dahlias, too, I’ve heard. How long do the cannas take to bake and what do you season them with? Your comment inspires me to think about planting a row in the vegetable patch. Never considered it before because they’re not great as cut flowers unless you lift the whole tuber with leaves and flowers attached, but now…
    Happy growing – cannas and everything else.

  • Greg Martin Said,

    I bake them until soft by the fork test. I season them as you would other baked root crops, usually tossing them in olive oil and some salt and pepper, or using a hot pepper oil if that’s desired.
    Thank you so much for the Dahlia tip…never heard that before. A quick web search brought up a Mother Earth News article on the subject:
    Can’t wait to try some of these!

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