Bringing Frost-Tender Bulbs Indoors for the Winter


When frost kills the foliage of your bulbs (here, dahlias), it’s time to bring them back indoors for the winter. Source:

Most summer-flowering bulbs other than lilies, and that includes dahlias, gladiolus, cannas, callas, colocasias, acidantheras and tuberous begonias, are considered “tender bulbs,” that is, they are not hardy enough to survive the winter in cold climates. Many of these bulbs may be able to overwinter outdoors in USDA zones 7–8, especially if well mulched (indeed, some gladiolus thrive in zone 6!) and certainly in zones 9 and above, but most gardeners living in colder zones can only keep them alive from year to year by bringing them indoors in the fall.


Gladiolus corms freshly dug up. Source:

Usually the signal to bring them indoors is when the first frost damages their foliage. If there is no frost before mid-November, though, bring them in any way: you don’t want them to be still in the ground when it freezes solid!


Let the bulbs (here, dahlia tubers) dry out for a week or so, then clean them up roughly before storing them. Source:

To do this, dig up the root ball and shake it to knock off excess soil, then let the bulbs dry on newspaper or cloth for a week or so in a frost-free spot (a garage or shed, for example). Now clean them roughly with a brush to remove most of the dirt. Don’t rinse them, though: they must stay dry.

On some bulbs, stems and foliage will fall off all on their own at this stage. If not, cut them off about 2 inches (5 cm) from the bulb. Also cut off any lingering roots and remove any bulbils (baby bulbs). (You can save the bulbils if you want, but be forewarned that they are usually 3 to 5 years from blooming!) You can also sprinkle garden sulfur on the bulbs: this will help prevent rot over the winter.

Make sure you properly identify your bulbs at this point. There is nothing more confusing than looking at a pile of gladiolus corms or dahlia tubers in the spring and trying to remember which were the red ones and which were the yellow ones! Either write the name on their storage container or add a label. Some people write the name on dahlia tubers with a felt pen!


You can layer bulbs one on top of the other as long as you cover the previous layer with vermiculite, peat moss, wood shavings, or shredded paper. Here, the first layer of dahlia tubers was covered in peat moss. Source:

If possible, store the bulbs in a cardboard box or a plastic container (the latter should be have holes so there’ll be a bit of air circulation), covering them with vermiculite, peat moss, wood shavings, or shredded paper. Some gardeners like to store them in a mesh bag.

The ideal location for winter storage is a cool but not cold spot that remains between 40 and 55˚ F (5–12° C) for much of the winter. That means that a fridge or a cold room may be too chilly for some tender bulbs, but a basement or lightly heated garage should work well.

You have nowhere cool to store them? Don’t worry: they can be kept at room temperature if necessary, but if so, the bulbs will tend to dry out over the winter, so check them monthly, giving them a spritz of water if they start to shrivel.


If you grow your bulbs in containers, you can simply pile the up in a cool, dry spot. Source:

One final note: if you grow your tender bulbs in containers, overwintering is even simpler. Just bring the pots indoors, cut off the foliage, let the soil dry out, then pile the pots up in cool, dry spot until spring.

Storage Temperatures for Tender Bulbs


At what temperature should you store your tender bulbs? Source:

You’ve brought your tender bulbs (gladioli, tuberous begonias, dahlias, cannas, caladiums, etc.) in for the winter? Perfect! The bulbs are either in their original pot or bare root, surrounded by peat, vermiculite, newspaper, etc. Also perfect! Now where to place them for the winter?

On the Cold Side

The ideal location for winter storage is cool, but not cold, between 40 and 55 °F (5 to 12 °C). That means a refrigerator or a root cellar is generally too cold for bulbs, but a barely heated basement or protected garage ought to be ideal. At such temperatures, there will be little evaporation and that will allow the bulbs to stay dry yet well hydrated until spring. There should be no need to humidify them in any way.

On the Warm Side

You don’t have a cool spot where you can store your bulbs? I don’t either … and that’s not a problem! You can easily store them at room temperatures as well. However, warmer air means there will be evaporation and probably some dehydration. That means you’ll have to take an extra step and moisten them occasionally through the winter.

I recommend a monthly inspection, followed by rehydration if needed.

How to handle this inspection, though, depends on how the bulbs are stored.

In Pots or Loose

For example, I store many of my tender bulbs in the same pot they grew in all summer. If so, you can’t really examine the bulbs themselves, but you can take a look at the soil. If it’s very dry, add just a dribble of water, say a few teaspoonfuls, to the top. Let the water penetrate the potting soil (that may take a few minutes, as very dry potting soil will repel water at first), then store the pot away again.


If .loose bulbs (here, dahlia roots) look dehydrated, simply spray lightly with plain water. Source:

If the bulbs are loose (bare root), you really can inspect them individually. If they don’t look shriveled (often the case during the first months of storage), they’re doing fine: just put them back. If, on the other hand, they’re turned soft or starting to shrivel, just spray them with clear water and put them back into storage. This tiny amount of water will be enough plump them up again and prevent a potentially fatal dehydration.

A Reminder


Add “check bulbs monthly” to your agenda. Source:

As soon as you bring your tender bulbs indoors in the fall, add a monthly note to your agenda: “check dormant bulbs, moisten as needed.” Mine is electronic, so beeps at me to let me know when it’s time. You don’t have to be precise: check them a week early or a week or two late, but do give them a look-over.

As you can see, when tender bulbs are dormant, they’ll adapt to almost any non-freezing situation. Finding the right place to store them couldn’t be simpler!