Do Canna Lilies Spread Out or Stay in One Place?
Canna lilies bring bold tropical blooms to the garden. But how much room do they need and what does their growth pattern look like? Find out if these dramatic blooms will naturally spread in the garden or need to be replanted every year!
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With towering foliage and dramatic blooms, some plants can make your garden feel like an oasis. Canna lilies are one of these, but you might wonder if they spread uncontrollably.
These lush subtropical or tropical perennials attract hummingbirds, bees, and butterflies, all while beautifying your garden – but we don’t want them to completely take over!
These lilies grow from a rhizome, which might be confusing because “bulb” is a widespread term used for lilies. Depending on your region, they can be long-lived. Let’s discuss the difference between the two growth systems and how rhizomes play a huge part in how much they spread.
The Short Answer
These plants spread via rhizomes, which are underground stems that put out adventitious roots. Each rhizome has growing points called eyes. Every eye will produce additional underground growth. Essentially, the more eyes, the more shoots that can potentially grow.
When you purchase these plants, the description will often say 2 / 3 eyes or 3 / 5 eyes. This gives you an idea of how many shoots will sprout. Each time a new shoot emerges, the rhizome also grows. Over time, the rhizome gets bigger and produces more eyes. In this case, the short answer is yes: canna lilies can spread as they grow.
The Long Answer
These expansive plants are ideal if you are looking for a plant that will spread and fill an empty spot. If you are planting in a garden bed or container, give them plenty of space.
There are a wealth of canna lily varieties that look great in many garden settings. Their brilliant flowers bring an array of colors to a sea of green. Overcrowding will affect flowering and foliage production, so even once they’ve hit the maximum space you’ve allotted, you’ll still need to thin out plants intermittently.
Rhizomes are the reason for their spread. This section will go in-depth on how they work.
Rhizome vs. Bulb
Bulbs and rhizomes are very different, with different internal structures and different orientations. Rhizomes are underground plant systems that hold nutrients and produce shoots and lateral roots.
These are essentially underground stems that are thicker than the growth that occurs on the surface and may best be envisioned by thinking of a “hand” of ginger (which is also a rhizomatic plant).
Rhizomes are starchy, with white flesh on the inside and eyes on the outside. In contrast, bulbs have a teardrop shape and grow sprouts through their top. They do not spread underground, although some bulb species develop offshoots, miniature versions of themselves.
Others will split into two or more separate bulbs as they mature, which is a bulb’s form of self-propagation (other than any seeds it may produce). Understanding the difference will help you understand the canna lily’s spread as it grows.
Growth Habits of Rhizomes
Rhizomes extend horizontally, sending out new roots and shoots from nodes. Nodes are where the new root growth occurs. Roots will grow from the bottom part of the rhizomes, and shoots will grow from the top.
Rhizomes are the storage unit for the plant. It’s important to protect them from damage. As the rhizomes grow throughout the season, they turn into a larger mass.
Eventually, the original rhizome you planted will be suffocated by new ones. If your climate is too cold for the rhizomes to overwinter in the garden, you may want to remove the rhizomes in the fall carefully.
Be sure to divide them into smaller segments before storage. Allow any cut surfaces to dry out and scab over before storage. When dividing, verify that each section has two to five eyes. Discard any thin, light, or rotten rhizomes.
Spacing During Planting
Consider your plant spacing. As these will spread gradually over time, leaving enough space is essential for growth. You will want to leave a foot or more between each rhizome.
Consider leaving extra space if planting a chunk with five or more eyes. Smaller rhizomes should still have at least 12 inches of space between each other. If you are planting in a container, consider your container’s size. A rhizome in a small pot may need to be replanted quickly, whereas one in a larger container will gradually fill the container.
Avoid planting more than 1-2, even in a relatively large container. Examine them before planting and count the number of eyes. This gives you a rough idea of how many shoots will grow and how full your container could get.
Overcrowding
As the plants grow, they may become overcrowded due to their fast-growing habit. This is a common problem and nothing to fret about. Following proper spacing during planting will delay overcrowding.
If your plants are too crowded aboveground, consider trimming off emerging shoots at the soil level to help with density. Another option is to remove a few of the rhizomes. You can cut and transplant them to a new location or discard them.
If you live in USDA zones 8-11, thinning at least every two years is recommended. This will help with overcrowding, and you can remove older, weaker plants.
Seeding
If allowed, these flowers will produce seed. The seeds form in a thick pod. When mature, the pod bursts and drops the seeds onto the ground below.
Typically, the seeds overwinter in the soil, then pop up the following spring; for people who already have a dense stand, this self-sowing habit can become a problem. Reseeding is a problem in zones 8-11, where the soil does not typically freeze.
This is less common in zones 3-7, but many varieties tolerate at least a small level of natural cold stratification and may survive the chilly months.
If grown in their ideal conditions, the rate of spread might surprise you! To prevent reseeding, remove the flowers once they fade but before the plant develops its seed pods. This helps control spreading.
Final Thoughts
If you are planning on growing canna lilies, it’s crucial to understand how they spread. Proper spacing at planting time may save you a lot of hassle later in the summer.
Prevent overcrowding by deadheading spent flowers, and if a plant becomes too packed in its container, divide it and share it with your family and friends!
