Canna lilies are noted for being pest and disease free. Well, for the most part! Like all plants, they can and do develop problems in the right conditions. Canna lilies love hot and humid climates and these types of conditions are more susceptible to diseases.
You don’t have to live in hot and humid regions to experience problems with canna lilies. Cold regions have their own problems as well. Your region is going to have an impact on the types of issues you encounter. Disease or pests might be present in one region but not another.
But don’t fear! Most of the problems canna lilies experience are preventable. If they’ve already taken place, most have a solution. Today, we’re going to talk more about some common canna lily problems and how to fix them.
With their big, tropical-looking leaves and showy blooms, canna lilies make a stunning addition to flower beds and borders But their rapid growth from rhizomatous roots can lead to them spreading out of control. If left unchecked, canna lilies will march across your garden in just a few seasons
While their vigorous spreading habit is great for mass plantings, it can be a nuisance when canna lilies invade lawn and planting areas. So how do you stop canna lilies from aggressively expanding their territory?
Why Canna Lilies Spread So Much
Canna lilies grow from thick underground stems called rhizomes. These rhizomes continuously produce new shoots and roots, expanding the plant’s footprint.
In ideal conditions, each canna lily plant can spread 1-3 feet outward every year. Over time, this leads to impenetrable patches of canna lilies that crowd and choke out other plants
A few factors enable such rampant spreading:
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Rhizome Growth – The rhizomes rapidly lengthen and branch to colonize soil.
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Underground Runners – New rhizomes shoot off the main one, spreading the plant sideways.
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Dense Foliage – Broad leaves shade and overwhelm nearby plants, taking over space.
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Separating Clumps – Rhizomes break off clumps that root separately when disturbed.
Without containment measures, canna lilies will keep extending their territory year after year through these mechanisms. But several strategies can limit their spread.
Effective Ways to Stop Canna Lily Spread
It takes diligence and discipline to rein in canna lilies’ tendency to spread far and wide. But here are the most effective methods to stop them from taking over:
Plant in Containers or With Barriers
Physically containing canna lily roots is the simplest solution. Plant them in pots and containers, or install vertical root barriers around garden spaces.
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Pots and Planters – Restrict spreading by growing canna lilies in containers and moving pots around.
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Plastic Edging – Sink 12-18″ plastic edging into soil to block rhizomes from traveling past walls.
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Concrete Lining – Pouring a concrete curb or footer around planting beds makes an impenetrable barrier.
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Pond Liners – Bury flexible pond/pool liners around beds to create an underground rhizome barrier.
Containment limits the expanded growth of canna lily root systems. Just be sure to leave ample room for growth within the confined area. Crowding triggers more rhizome spreading.
Aggressively Divide and Replant Annually
If planting in open garden spaces, you must dig and divide canna lily clumps each year. This prevents overcrowding and renewed spreading.
In early spring:
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Dig up entire clumps and wash off soil to expose rhizomes.
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Break clumps into smaller individual plants or 3-5 rhizome chunks.
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Replant chunks 2+ feet apart in well-prepared soil to discourage spreading.
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Discard excess pieces or pot up extras to gift or sell.
Yearly division eliminates overcrowded clumps prone to spreading. It also rejuvenates growth. But it’s labor intensive!
Cut Back Foliage in Fall
Cutting back canna leaves and stems after they die back in fall may reduce rhizome spreading. The theory is that removing foliage stresses the plant, limiting rhizome growth.
Research is limited, but it’s an easy extra step to try. Just be sure to mulch roots well for winter protection after cutting back spent foliage.
Grow Alternative Spreading Plants
Sometimes it’s best to simply avoid persistent spreaders like canna lilies. Instead opt for better-behaved flowering plants like:
- Daylilies
- Lavender
- Salvia
- Verbena
- Marigolds
- Zinnias
These spread slowly or not at all, saving you from constant division and containment efforts. A little planning prevents problems down the road!
When to Divide Canna Lilies to Control Spread
If you must divide canna lilies to restrain their growth, timing is key. Follow this annual schedule:
Fall – Cut back foliage once it browns after frost. Mulch roots.
Early Spring – Dig and divide clumps, discarding old rhizomes. Replant divisions.
Summer – Let plants grow and flower freely within space allowed.
Next Fall – Cut back and mulch for winter. Repeat process.
Dividing just once a year prevents crowding and signals the plant to slow rhizome production. Digging up cannas too often stresses the plant and may increase spreading.
Dividing Canna Lily Clumps Step-By-Step
Executing the canna lily division process correctly minimizes disruption to the plant while controlling spread. Follow these steps:
1. Cut Back Foliage
Start by removing all aboveground foliage in fall once it browns. Cut stems about 4 inches above soil level. Allow the dying foliage to reabsorb nutrients.
2. Loosen Soil and Lift Out Clump
Use a spade to loosen soil across the surface of the clump. Then leverage the shovel beneath the entire clump to lift it from the ground.
3. Remove Soil and Expose Rhizomes
Wash or shake off excess soil clinging to rhizome roots. Gently remove remaining soil with hands to reveal rhizomes.
4. Divide Clump Into Pieces
Break the root mass into smaller, more manageable chunks using your hands or a knife. Aim for individual plants or 3-5 rhizome pieces.
5. Inspect and Discard Unhealthy Rhizomes
Check each divided chunk for signs of rot or damage. Discard any diseased or overly small/weak sections. Keep only robust, healthy rhizomes.
6. Replant Divisions Properly Spaced
Replant the healthiest rhizome divisions in prepared soil, spacing them 2+ feet apart to prevent crowding and deter spreading underground.
7. Water and Mulch Transplants
Water newly planted divisions well and add mulch around each one. Stake larger plant sections if needed. This reduces transplant shock.
Follow this routine each spring to keep canna lilies under control. The key is preventing overcrowded clumps, which triggers more rampant growth.
Best Ways to Plant and Care for Canna Lilies
Even with division, canna lilies grow best when properly planted and cared for:
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Prepare planting beds with rich soil and good drainage. Cannas hate wet feet!
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Ensure full sun exposure. At least 6 hours daily is ideal.
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Water 1-2 inches per week. Increase watering in summer heat.
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Stake tall varieties and mulch around the base.
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Fertilize monthly with a high phosphorus formula.
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Prune spent flowers to encourage more blooming.
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Dig and divide crowded clumps each spring. Discard old rhizomes.
A little TLC keeps canna lilies healthy yet restrained in their spread. Pay attention to proper planting techniques, frequent division, and care.
Do Canna Lilies Die in Winter?
In zones 8-10, canna lily rhizomes can remain in the ground over winter. They go dormant once frost kills the foliage and will resprout the following spring.
But in colder zones 6-7, rhizomes dug and stored over winter have higher survival rates. The rhizomes perish below 10°F.
To overwinter canna rhizomes, follow these steps:
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Cut back and dig up rhizomes after frost.
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Allow clumps to dry for a few days.
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Remove dead foliage and roots. Keep only healthy rhizomes.
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Pack in damp peat or vermiculite. Store above 40°F over winter.
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In spring, divide and replant the renewed rhizomes outside again.
Proper rhizome storage prevents cold damage and death in harsher climates. In warmer zones, established canna lilies are very resilient through winter dormancy.
Are Canna Lilies Invasive?
While canna lilies spread readily, they are not considered an invasive plant in most regions. True invasive plants like Japanese knotweed colonize and damage native ecosystems.
When contained properly, canna lilies are unlikely to escape cultivation and cause harm. Just be sure to responsibly manage and dispose of any excess divisions.
In USDA zones 7-10, canna lilies behave themselves when grown under the right conditions. There’s no need to avoid planting canna lilies, just exercise smart control methods.
Stop Canna Lilies Taking Over Your Garden
Left alone, canna lilies will quickly outgrow their bounds and encroach upon your entire garden! That’s why keeping their
Rhizome or Root Rot
To prevent fungal growth, thin out the cannas every few years and replant them to a new location.
Rhizome rot, which is also called root rot, happens in soils that don’t drain well and get too much water. A fungus known as Sclerotium rolfsii and fusarium spp is what causes the rhizomes to rot. The fungus spreads from the base of the plant up the stem and is cottony in appearance.
If you notice rhizome rot, remove the infested plant and the root mass. To prevent rhizome rot in the future, thin your canna lilies every few years. Planting them in a new location after lifting will help prevent fungal growth.
Rust appears as red-brown spots on the leaves and spreads fairly quickly.
One of the most common diseases you’ll find on canna lilies is rust. The rust produces spores that move through the air or by water. The rust is powdery and red-brown in color. For a long time, this disease can grow on plants when it is humid and there is water on the leaves.
Rust spreads quickly and is hard to control once it gets going. There are a few ways to remove rust from infected plants. Remove all infested leaves, stems, or even whole plants. By removing plant parts or whole plants, you can mitigate the spread of the disease.
Botrytis mostly occurs in cold, rainy weather as a gray mold.
This particular blight affects the flower of canna lilies. It will appear as a fuzzy, gray mold. Botrytis blight thrives in cold, rainy weather and is commonly seen during the spring months.
If you want to control the spread of the blight, remove any infested flowers from the stem. Be sure to place the discarded flowers away from your garden and do not compost them. Blight can spread easily and overwinter on other plant material.
Rhizomes That Don’t Germinate
It is recommended to check each rhizome for the presence of eyes before planting.
You finally planted your canna lilies and it’s been weeks and nothing has germinated. This can be discouraging but here are some things to consider.
When planting the rhizomes, you may have planted dead bulbs. Before you begin planting look for thick, heavy rhizomes with 2 to 5 eyes each. If your rhizomes appear thin and mushy the chances are it’s not viable.
Each rhizome you plant should have eyes. During the dividing process, some rhizomes sections might not have eyes. Remember, eyes are the areas where shoots will emerge so we want plenty of eyes on the rhizome.
Another factor to consider is soil temperature. If you plant your rhizomes too early there is a chance of freezing. You will want to wait till soil temperatures are above 50ºF to plant. This will help prevent the rhizomes from turning to mush under the soil surface.
Water is also another factor in how well rhizomes will germinate. You should water your them daily until they begin to emerge. This will help hydrate the rhizome and encourage proper growth. Once they emerge you can water less frequently.
Common causes of yellowing leaves include overwatering, lack of sunlight, pests, and diseases.
What could be wrong with your canna lilies if their leaves are turning yellow? Usually, yellowing leaves are the first sign that something is wrong. Identifying why they are turning yellow can be a little more difficult. You will have to do a little detective work to determine the cause.
Common causes could be over or underwatering, not enough sunlight, or pests and diseases. Watering and sunlight are the usual culprits of yellowing leaves. Rhizome rot will turn the leaves yellow and then the leaves will die rather quickly.
It is recommended to plant the rhizomes at least 12 inches apart to avoid overcrowding.
There are a lot of leaves on the plant but no flowers yet in the middle of summer. What’s the matter? Canna lilies grow quickly and can get crowded if they don’t have enough room. Leave anywhere from 12 inches or more of space between each rhizome to allow for spreading.
Overcrowding will kill new shoots and prevent continuous blooms. As they spread, their canopy will start to close in and less sunlight can reach the soil surface. Those new shoots need sunlight to grow. If the canopy is too dense, the new shoots won’t have enough sunlight to continue growing.
If you believe your plants are too crowded, there are solutions. You can remove foliage that is finished blooming to allow sunlight for new growth. Also, you can dig up a few rhizomes to keep them from spreading more.
Five mistakes to Avoid When Planting and Growing Canna Lilies
FAQ
How to stop lilies from spreading?
How to stop plant roots from spreading?
How to keep cannas blooming all summer?
How do you prevent rhizome rot on Canna lilies?
To prevent rhizome rot in the future, thin your canna lilies every few years. Planting them in a new location after lifting will help prevent fungal growth. Rust appears as red-brown spots on the leaves and spreads fairly quickly. One of the most common diseases you’ll find on canna lilies is rust.
Can you leave canna lilies in the ground?
Leaving Canna Lilies In The Ground Anyone who lives in the warmer zones of 8+ can leave their canna bulbs in the ground over winter, as long as the soil doesn’t freeze. If you live on the cooler side of their hardiness zone, you can mulch them to give them extra warmth.
How do you get rid of canna lilies?
Since canna lilies grow from an underground rhizome, killing them is not as easy as cutting back the foliage. It may disappear for the rest of this season, but it will be back next year, as vigorous as ever. To permanently get rid of canna lilies, you must literally get to the root of the matter. Did you plant vegetables this year?
How do you overwinter canna lilies?
By far the most popular method of overwintering canna lilies is to dig up and store the bulbs. This is a must if they are planted in the garden. The nice thing about it is that there’s no rush to dig them up. You can leave them in the ground even after a hard freeze kills the plant.
How much space do canna lilies need?
Canna lilies spread rapidly and if they don’t have enough space they can become overcrowded. Leave anywhere from 12 inches or more of space between each rhizome to allow for spreading. Overcrowding will kill new shoots and prevent continuous blooms. As they spread, their canopy will start to close in and less sunlight can reach the soil surface.
Should you cut canna lilies in winter?
As winter comes around or a hard frost burns them up, don’t be afraid to cut the stems all the way to the ground. Canna lilies are one of those plants that’s bounds back to a full- grown plant come Spring, given the fact you are growing them in their proper zone, and they aren’t frozen to death.