Canna lily is known for its beautiful flowers. I have seen a lot of gardeners focusing on the blooms and not on the overall health of the plant.
In this article, I will guide you on what to do when canna lily leaves are turning brown.
To go with the remedy, please first identify the cause or causes, and I will help you identify them.
Causes - Canna Lily Leaves Turning Brown
Let's list the most likely causes first:
- Canna Leaf Roller
- Due to cold (Especially in winter)
- Due to heat and rain at the same time
- Canna rust
- Fungal issue
I will not talk about watering issues here. They can tolerate a good amount of rain, so overwatering won't be an issue unless the water drainage system is really bad.
Due to underwatering, the leaves will turn yellow first, and then they will show brown edges.
Note: On GardenVive, I always try to show you the causes with pictures. And I love to take pictures from my garden only. I need to collect multiple pictures at different times of the year. This process is time-consuming. I love to share what I learn. Subscribe to this site and become a member to help me present more gardening guides for you.
Canna leaf roller
Canna leaf roller is responsible for the leaves turning brown in most of the cases, and it's very easy to identify.
They wreck the leaves by sealing them together. You have to treat for them, or the cycle will never stop.
It's a nasty little caterpillar that rolls the newer leaves shut and leaves webbing and poo poo. Then damaged leaves end up looking like this, but early on you see little holes in the newer leaves.
How to identify?
If you witness rolled or tightly folded young leaves held together with fine silk, it's definitely due to the leaf roller.
They are actually the caterpillars of the Brazilian skipper butterfly.
They terrorized me a few years ago. They seem to be worse if the cannas are under an overhang or don't get rained on a lot.
What to do?
Spray BT. Spray both sides of the leaves (especially the undersides of the leaves).
Unroll one of the leaves and see if there are worms and poop inside. If so, spray with BT. My canna lilies are looking a lot better after a couple of BT treatments.
You can also treat with insecticide, or you can cut the bad leaves off and put them in tied garbage bags.
Canna leaves turning brown due to cold
In winter, this is very common to witness.
Canna lilies are tropical to semi-tropical plants. They go under stress when it's cold out there.
They do kinda get ratty during winter, and even some die back.
They can be chopped like a banana, but they’ll come back. Like most plants, they slow down a good bit or even almost stop growing in “winter” months, even in warmer southern FL climates, especially after cooler drying spells.
There was a very large almost forest of them at my old condos here, and in winter they looked ratty, and if it got cold enough they’d kinda just go brown, etc. In the ground and on the south side of a building, they’ll do better in winter but will still slow way down and even go dormant if it’s cold/dry enough.
You’ll probably want to cut back a good bit on watering now until we begin to warm up towards the end of winter.
You can cut them back if they get ugly. The rhizomes should be fine either way here since we don’t freeze, and some leaves may even stay viable since we don’t really frost either.
But this is their resting period now, and they should shoot right back after a couple months.
The brown spots on canna leaves might be a symptom of sudden cold.
If they are potted, bring them inside.
You can check this chart: when to bring plants inside in winter- chart
If your canna lilies are planted outside and you are from a colder region, cover them in winter. Here is another chart for you: when to cover plants in winter - chart
Due to heat and rain at the same time
Canna lily loves a tropical, humid climate and rain.
But in the rainy season, if the temperature is too high, canna lilies go under stress.
When the humidity is high, the chances of fungal attack are also higher.
If you look at the above picture closely, you can see some black spots as well.
A canna lily that has been infested with aphids or other sap-sucking insects is more likely to develop sooty mold or black coating. (actually a fungus)
What to do?
Spray fungicide and remove some plants if they are heavily crowded. You need to maintain good airflow between the leaves.
Brown spots on canna lily leaves due to rust
If the brown spots are like the above picture, you may have Canna Rust. It's been hard for me to eradicate in my earlier days of gardening.
I created a detailed guide on how to get rid of rust for Plumeria. The same treatment gonna work for canna lilies too.
You can check it here: How to get rid of rust
In short, Mix water and Hydrogen peroxide and spray it on your infected canna lily plant.
Due to fungal infection, you may witness brown or dry patches like this on the canna leaves.
You can use a fungicide. You can go for copper sulfate. But I do not use copper sulfate that much. It's not good for the soil if used frequently.
