Canna lilies are easy to grow, quick to propagate and relatively low maintenance. They're hardy perennials that bring a dynamic touch to the garden, with beautiful foliage and vibrant flowers in red, orange, yellow, pink and cream, plus leaves in green, bronze, burgundy, even variegated and striped. With hundreds of hybrids out there, there's sure to be a combination that suits your garden.
They're perfect as a dense filler, making an excellent privacy screen to block an unsightly fence, and they thrive in damp, boggy ground where other plants fail. Give them full sun for six to eight hours a day and keep the soil moist, and they'll flower right through summer until the first frost. That same vigour is worth knowing about before you plant. See the note at the end about keeping them out of waterways.
All that growth has to go somewhere, though. By the end of the season a clump looks tired, with spent flowers, brown-tipped leaves and weeds coming up through the stems. That's where pruning comes in.
Canna lily flowers
Striped canna lily leaves
How To Prune Canna Lilies
Before you begin, assess the task ahead. The plant is very hardy, and can handle a hard prune. The clump pictured below is approximately 1 metre square, which may seem like a large job ahead - however, they also grow well in containers around 20 to 25 litres, provided they have plenty of moisture.
When to Prune
The best time for a full prune depends on your climate. Where frost is a factor, wait until spring, after your last frost — the old foliage isn't pretty, but it shelters the crown through winter, and the mulch does the rest. In frost-free areas you can cut back in late autumn instead, once the clump starts to look untidy with spent flowers, brown-tipped leaves and weeds coming up through the stems.
Tools to Use
The plant is very hardy and the stems are very soft, so using an electric hedger works a treat. Depending on the size of your canna lily patch, handheld secateurs will work well for smaller plants. You could also use a machete, or a brush hook, depending on the size of your plants and what tools you have on hand.
Deadheading
As the flowers start to fade throughout spring and summer, deadheading the spent flowers can prolong the neat look of the plant. If deadheading, do not cut the entire stem off - simply follow the flowering stem down and you will likely see a new flower bud about to emerge from the lower leaf. Cut the stem just above the new emerging bud.
Initial Clearance - For Large Clumps
Your first pass at pruning doesn't have to be perfect, especially with a large clump. Simply shorten the stems, pull out any weeds, and clear away the cut foliage and debris so you can see what you're working with.
After the initial clearing
Checking For Disease
At this stage, assess your plant again for any signs of pests and disease. Common things to look for are orange spots on leaves - Canna Rust (Puccinia thaliae) or rot around the base (Rhizome Rot). Rust spreads more readily in crowded, humid growth, so thinning the clump and improving airflow helps. Rhizome rot is a different problem - it comes from soil that stays waterlogged rather than just damp, so check drainage if you find soft, rotting rhizomes at the base.
Clean Up
Once you have most of the stems cut back and you can see into the clump, you can use a rake and pull out the dead leaves and old growth. Now you can go in with your secateurs and trim the stalks down to roughly 10-20 cm from the ground - this will help tidy up the clump. Ensuring your cuts are clean will prevent disease from entering rough ended stalks, giving new growth the best start.
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Now you can see what’s going on in the root zone
Thinning (Optional)
This is also a good time to dig up any rhizomes (tubers, or roots) to thin out your plant, and to make new plants to give away to friends or start another patch in your garden. Lift a clump out using a garden fork or spade, shake or wash off any excess soil so you can see the rhizome. Check for eyes or buds and roots on the rhizome – this is your new plant. If the clump is too big, simply cut it apart with your spade or a knife. Just pop the rhizomes into a pot with some potting soil and water in. New shoots usually appear within a few weeks.
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Dead leaves raked out and loose stems trimmed
New shoots emerging at the base
Disposing of Trimmings
The trimmings that you have taken from your canna lily are perfect for green mulch; use it as a chop and drop mulch, or chop it up and add it to your compost bin.
Important
Be sure not to add any roots, rhizomes, or shoots into your compost bin or in your mulch. It's better to pot them up to make new plants or dispose into your general rubbish bin, as they can become invasive.
New growth after a few weeks
Tips & Observations
If your canna lily looks like it needs some fertiliser - using blood and bone, well-rotted manure, or a slow-release balanced fertiliser will work well.
Mulch around the clump to prevent weeds, and after a few weeks your canna lilies will be starting to sprout again.
The downsides of canna lilies? They can become an invasive weed in natural waterways, which can crowd out native plants due to their thick clumping growth. Therefore, it is very important to dispose of rhizomes and seeds thoughtfully. Your local council can provide further information.
Canna lilies offer a stunning, visual impact - with easy low maintenance. They are a hardy plant that is great for beginner or advanced gardeners, adding lush foliage and bright stand-out flowers for any space.
Article & Photographs by Natalea Erskine
