Canna Lily Overview
|Official Plant Name||Canna|
|Common Name(s)||Canna Lily|
|Hardiness Rating||H2 / H3|
|When To Sow||April, May, June|
|Flowering Months||July, August, September, October|
|When To Prune||October, November|
Full Sun / Light Shade
1 – 2M
0.1 – 0.5M
July – October
Most Soil Types
Moist but well drained
Canna lilies are vibrant perennials that can really brighten up a garden border or container garden.
Though tender, they can make beautiful summer bedding plants. The rhizomes can overwinter in milder, more southerly parts of the UK as long as they have a good covering of mulch. They can also be grown in a cool conservatory indoors during the summer months.
What are Canna Lilies?
Even thought they are commonly called Canna lilies, Canna are not actually lilies at all. They are actually a family of a number of species in the order Zingiberales. They are more closely related to gingers, bananas and arrowroots. Typically, in the UK, we tend to think of cannas as ornamental garden plants. And many cultivars have certainly been developed for their visual appeal. But cannas are also used around the world as an edible source of starch in food production.
Canna lilies, both ornamental and edible species, are native to tropical and sub-tropical regions of the new world, from the Southern US to northern Argentina. However, cultivars were mostly developed in temperate climate zones and can be grown throughout temperate zones as long as they get 6-8 hours of sunshine daily in the main growing season, and are protected from winter cold.
Canna lilies have beautiful flowers, usually in red, orange or yellow or some mix of these colours. Which is why they have become popular plants in horticulture around the world.
Why Grow Canna Lilies?
Most gardeners will grow canna lilies for their ornamental appeal. Their impressive display of blooms which can flower in your garden from June to October, and their large leaves, make these plants firm favourites for many garden schemes.
There are also varieties which can be grown for their starchy rhizomes. Which could be something to delve into more deeply if you are interested in forest gardening, or edible landscaping. Cannas can also be useful in organic, permaculture gardens for the generation of biomass, which can be used in mulching, composting, and returning nutrients to the soil. Cannas are also sometimes used in drawing pollutants for the restoration of wetland environment.
If growing canna for ornamental reasons, there are many modern cultivars and hybrids to choose from. These include the RHS AGM awarded:
- Canna x ehemannii
- Endeavour (water canna)
- Erebus (water canna)
- General Eisenhower
- Louis Cayeux
- Ra (water canna)
- Russian Red
- Whithelm Pride
Canna edulis/ Canna discolor is the species grown in agricultural cultivation.
Where to Grow Canna Lilies
Canna lilies can be grown in beds or borders, or in containers. Growing in containers in cooler regions means the plants can be taken indoors during the coldest part of the year. They will require a sunny and sheltered spot. Shelter is particularly crucial because the large leaves of the plants are often shredded by strong wind.
Most of the cannas on the list above are best grown in moist but well-drained soil. They require a chalk, loam or sand soil that is moderately high in fertility but will not become waterlogged. Remember, when choosing and positioning a canna, that these grow into large plants – some varieties can reach well over 2m in height. Smaller varieties may be better for growing in containers, but even these will typically grow over a metre tall.
Water cannas are a little different. These can grow in a moist and well watered border, or in a container placed in a basin of water. But can also be placed in pots into the shallow edges of a garden pond, as long as there is no more than around 15cm of water over their roots.
Planting Canna Lilies
Canna are grown from rhizomes (root sections). Cultivars will not come true from seed. If you do decide to take the harder route and grow from seed, note that cannas grown from seed will not flower, typically, until their second year.
Rhizomes are typically available for sale in late winter. In order to grow canna from rhizomes, gardeners simply place the root section into a pot of multi-purpose compost, with the rhizome just covered. This is usually done in March or April – as soon as conditions of 10-16 degrees can be maintained. If you have a conservatory or heated greenhouse, you can obviously start a bit earlier than those without heated growing spaces.
If you have missed out on planting rhizomes for canna lilies this year – don’t worry. Canna lilies can also be purchased as pot grown plants at any point over the late spring/ summer.
Canna lilies that have been grown from rhizomes should start to develop strong shoots in a matter of weeks. As the shoots develop, it is important to make sure that you keep up to watering your plants. Keep Canna protected and undercover until all risk of frost has passed in your area. Harden off and plant out around the end of May in most parts of the UK.
If you are growing your Canna in a bed or border of the summer, plant out at a spacing of around 75cm apart, and around 10cm deep. Mulch well around the plants with a good quality homemade compost or well-rotted manure.
If you are placing your Canna in containers, make sure that the containers you choose are at least 30cm wide. A John Innes no. 3 loam based compost will be ideal as a growing medium. Again, place the rhizomes around 10cm deep.
Summer Care for Canna Lilies
Caring for Canna lilies over the summer months is generally fairly easy and hassle free. You need to make sure that you provide plenty of water during dry spells. It is also a good idea to provide a potassium-rich organic liquid feed at midsummer.
Canna is sheltered spots should not usually need staking. But some support may be beneficial for particularly tall specimens, or for those grown in a slightly exposed spot.
One piece of good news is that Canna in the UK are rarely seriously troubled by pests or diseases. Just look out for the usual garden culprits – slugs, snails, aphids etc.. Though they can be annoying, these things are generally pretty easy to control in a well-balanced ecosystem of an organic garden. Rarely, the plants may develop a virus. Sadly, there is no cure for this and the infected specimens must be destroyed. But most canna growers experience few problems and find Canna relatively easy and trouble free to grow.
Problems of non-flowering which can arise are usually the result of trying to grow Canna in an unsuitable spot, starting to grow rhizomes too late, a lack of water or poor soil fertility. But take care of the soil, plant at the right time, and water well and you should not encounter issues.
Most Canna care over the summer months will involve taking a couple of simple steps to make sure that the flowers bloom for as long as possible. First of all, in is a good idea to deadhead the spent flowers, which will encourage more to appear. Once a particular flower spike stops budding, it is also a good idea to cut it down to the next side shoot. This should encourage a secondary flower spike to develop.
Winter Care – Overwintering Canna Lilies
In the winter, what you do with Canna over the winter will depend on where you live. In milder parts of the UK, it is possible to keep Canna in the ground all winter. But even in the mildest UK areas, it is important to take steps to make sure the rhizome is safe over the coldest months. You will need to apply a deep dry mulch of straw or autumn leaves or other such material over the area – at least 15cm deep. And be prepared that you may still lose your plants if the winter is particularly cold or wet.
Of course, if you are growing in a colder area, leaving rhizomes in the ground is not usually an option. If you are growing Canna in the ground, you should wait until the top growth of the plants begins to die back in autumn, then lift the rhizomes. The foliage should all be cut back to around 15cm, and the rhizomes should be dried and then stored in just-moist compost in a frost free position. No watering should be necessary in most cases.
If you are growing Canna in containers, things are more straightforward and you can simply move the containers under cover into a frost-free location. So growing in containers can be the easier choice if you live in a colder region.
Take care of your Canna over the winter and they can be placed back out into your garden to enjoy again next year, and over the years to come.