How to Overwinter Bulbs in Containers

Alocasia, alliums, amaryllis, canna lilies, colocasia, crocuses, daffodils, dahlias, hyacinths, irises, peonies, ranunculus, snowdrops, tulips, and many more can be overwintered in containers.

To clarify, not all of these plants technically grow from bulbs. Some have tubers or corms, but they can all be stored the same way.

The challenge with overwintering bulbs in containers is that if the temperatures are too warm, or there is too much direct light hitting the pot, the bulbs may start to come out of dormancy.

In addition, some species, like daffodils, crocuses, and hyacinths, require a period of chill hours to break dormancy in the spring.

Chill hours refers to the amount of time the bulb is exposed to temperatures between about 34 to 45°F, depending on the species.

Some species need an extensive chill period. Daffodils, for example, require up to three months.

Research your specific species to know what special requirements they might have, and if you’re overwintering them in containers, make sure you keep in mind their needs.

Whether you dig up the bulbs, corms, or tubers, or they are already growing in a pot, there are a few steps you need to take to keep them healthy and ready to thrive the following spring.

Here’s what I’ll cover:

Choose and Prepare Your Container

If your bulbs are already growing in a container, you can skip this section.

But if you are choosing the growing container or moving your plants from the ground to a pot, you’ll need to do some preparations.

Pretty much any type of container will work. It can be a nursery pot or a fancy cement one.

The one requirement is that whatever pot you choose must have one or more drainage holes. If moisture builds up inside the container it can cause your bulbs to rot.

Next, make sure that the container is clean. If you’re reusing an existing pot, be sure to wipe it down with hot, soapy water or a 10 percent bleach solution (one part bleach to nine parts water) before use.

Then, get your hands on an appropriate potting mix for the species you are growing.

In-Ground Bulbs

You can remove tender bulbs growing in the ground and put them into a container to protect them during cold winters.

You don’t need to dig up species that are hardy enough for your USDA Hardiness Zone.

Digging up the bulbs generally should be done just before the first freeze of the season. You don’t want to dig them up too early, but you don’t want to wait until it has become too cold or the ground has frozen, either.

Start digging straight down, leaving a perimeter of four to six inches around the foliage. Dig about six inches to a foot deep, depending on the species.

Daffodils and tulips tend to be fairly shallow, while crocus corms can be quite deep, for example.

When you’ve dug around the entire perimeter, gently lift up the clump and knock away the soil to locate the bulbs. Clean them with a soft brush, being careful not to cause any damage.

Set them aside in a cool, dark area where they can cure for a week.

Now, you can fill the container with a suitable potting mix and bury the bulbs at the appropriate depth and spacing for the species, but don’t water! The goal is for them to stay dormant until you’re ready to wake them up in spring.

You can leave the pots outside if it’s warm enough for the species and if your winters aren’t too wet. If it rains often and the potting medium will be constantly soggy, or if the temperatures drop too low, store them in a garage, unheated basement, or shed that stays above freezing.

The benefit of this method is that they’ll be ready to take outside as soon as spring rolls around and you can choose to keep them in the container or remove the bulbs and put them into the ground.

For gardeners who live in an area with a short growing season, you can jump-start growth indoors in early spring by moving the container next to a south- or west-facing window and adding a small amount of water.

When the temperatures are high enough for the species you’re growing, you can take the container back out to their growing area and either replant them in the ground or keep them in the pot.

Potted Plants

If your plants are already in containers, the winterizing process is much easier.

For tender species, all you need to do is wheel or move the container to an unheated garage or basement. A shed or greenhouse will work, too.

Essentially, you want to find a place that will stay around 40 to 55°F but won’t even drop down to or below freezing.

Move the container back outside as soon as the weather is warm enough for the species you are growing, typically above freezing for tender species.

For species that require chill hours, you can simply leave the container in place assuming that your climate is appropriate for the species. If not, you’ll need to move the container to an area that drops just below freezing but not colder than the bulbs can tolerate.

This might mean moving to an unheated garage or shed. Sometimes a spot next to a south-facing brick wall is warm enough because of the heat that is absorbed by the wall when the sun shines on it.

When the temperatures are consistently warm enough for the species, you can move the pot back to its usual spot. You’ll rapidly see green shoots develop.

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