Digging Canna Tubers: How And When To Dig Up Canna Bulbs

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Canna lilies can bring a lot of color and personality to your garden, thanks to a long blooming period and attractive but straightforward foliage.

However, while these plants are technically perennials, you will usually have to dig them up each year.

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This is because the rhizomes need to be overwintered like bulbs (which is why they’re often called bulbs erroneously). 

Here’s everything you need to know about when and how to dig up those rhizomes so your cannas can be at their best each year.

How And When To Dig Up Canna Bulbs?

Cannas need to be dug in the fall up for rhizome division and overwintering.

The process is simple but may not need to be done every year, depending on your zone, and the cannas are potted.

When To Divide

Canna rhizomes need to be divided every 2 to 3 years to reduce overcrowding and remove the older central portion of the clump.

Most growers will divide when they uproot the plant for winter storage.

However, in cases where the plant doesn’t need to be uprooted (such as in warmer zones or when they’re kept in containers that can be brought indoors), the division is still best performed in the fall once the foliage dies back.

Do I Need To Dig Up Cannas In My Zone?

Cannas can handle a bit of cold but aren’t frost tolerant.

In USDA hardiness zones 10 to 12 (as well as parts of zone 9b), the ground never gets cold enough to damage or kill the rhizome so that you can leave them in the ground.

Depending on the species or cultivar, your plant may be a little more cold-hardy, in which case they can be left in the ground with a thick layer of protective mulch in zones 8 to 9.

Suppose you have a less tolerant plant or live in zones 7b or cooler. In that case, you’ll need to uproot the rhizome annually and overwinter it indoors.

Preparation: What You’ll Need

Only a few tools are needed, and most can be substituted for something similar:

  • Gardening fork and/or shovel
  • Cloth or small tarp (optional, but makes things less messy)
  • Bleach
  • Water
  • Paper (newspaper or paper bags)
  • Cardboard box
  • Peat moss

Step 1: Cut Back The Cannas

Regardless of where you live or where the canna is planted, you will need to cut it back once the leaves begin to die off.

Taller cannas should be cut to around 3” inches above the ground, while dwarf canna plants can be cut back to about 2” inches.

Container plants that can be moved indoors are generally cut back to the soil level.

If you live in a warm enough zone, this is where you can stop unless it’s time to divide.

Just be sure to add enough mulch to cover the stalks if in zones 8 to 9.

If it’s a dividing year, continue with Step 2.

Step 2: Excavate and Clean

Move around 6” inches away from the base of the plant and put your fork or shovel in the ground, aiming straight down.

Work your way around the plant until you’ve created a complete circle.

Now insert your digging tool and gently pry the clump out of the soul, letting it top onto the tarp or cloth you’ve laid out.

Gently knock off any loose dirt to expose the rhizomes, careful not to scratch or nick the outer surface.

You can also use a hose to spray the dirt off.

Step 3: Divide

Take a good look at the rhizomes and begin planning where you want to separate them.

Each rhizome chunk will need to have at least three eyes and should be healthy.

Look for any soft and discolored spots which will need to be discarded.

You can use sharp, sterile shears, scissors, or your hands to break off each section.

Remember to discard the central rhizome, nearing the end of its prime.

Rhizomes are solid and starchy on the inside like a potato, so check for any signs of disease and discard infected bulbs.

Soak each healthy rhizome in a solution of 1 part bleach to 9 parts water for about 30 minutes, then allow them to air dry somewhere with indirect sunlight for 2 to 3 days.

You can either replant the separated rhizomes (in zones 10 to 12 or if in containers) or continue with step 4 for overwintering.

Step 4: Curing Bulbs

For rhizomes that need to be overwintered, continue air-drying them for seven days.

You don’t need light for this, so Cannas can be stored in a warm closet or garage while curing.

This process helps remove excess moisture that could otherwise lead to rot over the winter months.

Step 5: Overwintering

  • Once fully cured, wrap each rhizome in a bit of newspaper or a small paper bag.
  • Lay the little packages in a cardboard box, ensuring they’re in a single layer.
  • Add a bit of dry peat around the containers.
  • This provides a bit of insulation and will also draw away any leftover moisture.
  • Place the box in an excellent, dark spot such as the garage, making sure the temperature remains at around 40° degrees Fahrenheit throughout the winter months.

Check out this article for details on overwintering potted canna lilies.

Note: Canna Rhizomes Need Checking

While the process of overwintering a canna rhizome is similar to that of bulbs, it’s important to remember that they are NOT bulbs.

As a result, you will want to check them every few weeks for signs of rot.

If caught early enough, you can cut away the brown section, leaving only the healthy white flesh.

However, you may find it necessary to discard the entire rhizome if there’s a lot of rot.

They will also need another thorough inspection in the spring when you’re ready to plant.

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