canna They be beat!
Spoil your cannas with the richest soil, like does, and they will give you a spectacular show even in the harshest conditions
THIS summer may have been tough for a lot of plants – not to say their gardeners – but a few seem to have relished every hot, dry second and none more so than my cannas.
Cannas come from the West Indies and sub-tropical South America and so have evolved to take more heat than we can ever throw at them.
In fact, most problems with growing cannas come from cold temperatures as they are not really hardy and, except in the very warmest spots on our islands, I always recommend lifting them and storing the plants in a frost-free place over winter.
The surprising thing this year, though, is that they do not seem to have objected to the drought.
Conventional gardening wisdom has it that cannas need lots of water – and certainly they will grow quite happily in a bog or even submerged in the margins of a pond. But I have not given any of our cannas growing in the borders a drop of water this summer, and they’re still doing well.
Cannas are extraordinarily adaptable and are not fussy about soil type, or whether it is acid or alkaline, and a good rule is that if you can keep a dahlia happy then a canna will thrive in the same situation, be it full sun or dappled shade.
It is true, though, that the richer your soil the happier and more floriferous cannas will be.
You really cannot overdo this, and that is why they have been so happy in our borders this year.
The soil of our Jewel and Cottage Gardens is a marvellous clay loam to start with and then has had a quarter of a century of me piling on compost and manure. It is oligarch rich. The few cannas that I grow in pots are potted up in almost pure garden compost and they love that too – although these containers are watered copiously.
You may not be able to replicate those conditions, but at the very least your cannas should always be generously mulched after planting and never be allowed to dry out if they are to flower well.
The combination of their vivid, flamboyant flowers and enormous, striking foliage makes cannas one of the most dramatic plants in any garden.
I particularly like the mixture of dark or striped foliage with brilliant flowers in ‘Wyoming’, which has orange flowers, ‘Black Knight’, which has red blooms, or ‘Durban’, which has chocolate leaves and orange flowers.
‘Australia’ is enormous – my specimens are certainly too big for the pot I first planted them in – but is perfect at the back or centre of a large border to up the ante when it comes to pure extravagant lushness.
Each flower only lasts a few days but more will be produced from the same flower spike until there are no more buds.
It should then be cut back to the next side shoot, where a secondary spike will appear.
Most cannas will produce three or four spikes by the end of the season. They tend to produce flowers after the seventh leaf and if they stop growing after the fourth or fifth leaf and therefore do not produce any flowers, then that is a sure sign that they need feeding.
Fish, blood and bone or liquid seaweed varieties of feed are ideal.
Although a sudden hit of frost will damage flower stems and foliage, the rhizomes are likely to be unaffected so the plants can still be lifted, the frosted parts cut back, and then stored over winter.
Canna roots are fleshy and store enough food to take the plant through its dormant winter season but they must not be allowed to dry out.
I put them into pots just big enough to contain the roots, pack them with spent potting compost and store them in the cool (but frost-free) greenhouse, watering them lightly once a week to stop them drying out.