Canna lilies are beautiful flowering plants that people love, but one of the challenges to growing them is that they can spread rapidly underground, causing overcrowding. To keep the rhizomes under control, divide the plants every few years and stop them from spreading.
If you live in certain USDA growing zones, you may have to dig up the rhizomes every winter to avoid overcrowding, but regardless of how often you do this, below are the steps you need to take to make it a success.
How to keep canna lilies from spreading
Here are the 8 simple steps to stop canna lilies from spreading in your yard and taking over the space.
Step 1: Cut the cannas back
To get started, cut the lilies back just a few inches above the soil. Do this in the fall after the active growth period is over. It is best to wait until the whole stem is brown. The rhizome will reabsorb the nutrients from the stems to strengthen the rhizome.
If you live in an area that is prone to frost, such as USDA growing zone 8, you should wait until after the last major frost when the leaves die so they can photosynthesize and push as much energy as possible to the rhizomes.
Step 2: Cover the stems with mulch
Cover the exposed stems of the plant using 4-12 inches of organic mulch. This will insulate both the soil and the rhizomes and help them get healthy. The warmer the area where you live, the less mulch you’ll use.
For example, if you live in zone 10, you’ll want to use only 4 inches of mulch. In areas that are not as warm, you can use up to 12 inches of mulch.
If you live in a very cold region you can dig the rhizomes up in fall and store them in a mix of coconut coir and mulch. Keep this moist and store it in your garage until the weather warms in spring. You can then plant them out in a new space.
Step 3: Dig up the rhizomes in spring
If you are leaving your rhizomes in the ground over winter, in early spring, dig up the rhizomes after the last expected frost. Take a spade and push it into the soil just a few inches outside of the exposed plant stems. Then dig up your rhizomes in one large section or several large clumps.
Step 4: Remove the excess soil from the rhizomes
Once the clumps are out of the ground, shake them gently to remove any clinging soil or debris. If you want to, you can spray the soil with a hose so that the rhizomes are much easier to see. The goal is to make sure that you have just the rhizomes and no debris of any kind attached to it.
Step 5: Pull the canna lily rhizomes apart
Take the clumps of rhizomes and pull them apart gently until there are three or four sections of them. This will make all of the rhizomes are easier to see. You should also look to see if there are any “eyes” on the rhizomes, which are growth points or nodules.
Step 6: Break the rhizomes into pieces
Once again, take the rhizomes and break them up into smaller sections. In the end, you’ll want to make sure that each of the three or four sections has a minimum of three eyes. Use a sharp knife to break apart the rhizomes if you have to.
Some of the rhizomes will be difficult to break apart without this. If any of the rhizomes seem very small, show signs of rot, or are weak, go ahead and discard them.
Step 7: Clean them with bleach (optional)
At this point, put together one part of chlorine bleach and nine parts water. Use this diluted bleach mixture to clean off each of the rhizome sections so that you can kill any diseases they might have. Clean them well, then rinse them off thoroughly using tepid water.
Step 8: Plant the rhizomes back into the soil
Take each of the sections of rhizomes and plant each of them 4 inches deep and 30 inches apart.
They need plenty of room in order to reach mature size. If there is not enough room in your original flower bed, find a new space or plant them in pots to give them plenty of room. This will give them the room to grow to their full potential.
To start a new flower bed, plant the individual rhizomes in pots with 12-inch diameters, or simply discard the remaining rhizomes.
Tips to Grow Great Growing Canna Lilies
Canna lilies are not difficult to grow, but the following tips can make growing these magnificent plants even easier:
Canna lilies can handle a lot of different soil conditions as long as they drain properly. That being said, rich soils high in organic matter with a pH of around 6.5, will work best when growing your canna lilies.
Canna lilies can survive in part shade but do best in full sun.
Temperature and humidity
The plants are sensitive to frost and colder temperatures yet thrive when it gets up to 90 degrees Fahrenheit. If you experience cool temperatures during the spring months, it might take a little longer for the canna lilies to start growing. They also do better in more humid conditions because this is what they’re used to.
Canna lilies are heavy feeders, so feeding them every month, or at least twice during the growing season, is important. Make sure that you’re using a fertilizer that is high in phosphorus, such as 5-10-5, so that blooming is encouraged. Also, use lots of organic fertilizer or compost so the plants get all of the nutrients they need.
Finally, you should water your canna lilies one or two times per week. The soil needs to be evenly moist but not soaking wet, which can lead to rot. Do not overwater or underwater the plants.
Canna lilies bloom in the summer and are available in beautiful colors such as orange, yellow, red, pink, white, and ivory. They do best in USDA growing zones 7-10, and they are available in ten different species and cultivars that include Shenandoah, Pretoria, Stuttgart, and King Humbert, among others.
Canna lilies are not difficult to grow, but they do have rhizomes in the soil that spread rapidly and cause overcrowding. Because of this, it’s best if you dig up the rhizomes and break them into sections, then replant them in additional flower beds. When this isn’t done, the rhizomes can actually choke the soil and affect the way the flowers grow.
It isn’t that difficult to break up the rhizomes and replant them, and if you follow the simple directions above, your canna lilies should be easy to keep growing for as long as you wish to enjoy them.
I am an accredited practicing dietitian, experienced gardener and a dedicated cook. I love writing and sharing my experience so you can learn from my successes and mistakes.