© Janet Davis
Despite earlier
reservations, I’ve become a lover of canna lilies. In fact, I’m the proud mama
of my very first—an elegant number with slender red flowers that I bought to
plunk in an antique iced-tea urn from Quebec (don’t ask) whose soil stays too
wet for most plants to thrive. Pride of
municipal parks, beloved by fussy Victorian gardeners and now enjoy
ing
a BIG renaissance, canna lilies are tender rhizomatous herbaceous perennials that
are native to tropical and subtropical parts of South America, Asia and North
America, and have their very own botanical family (Cannaceae). The name comes
from the Greek word kanna or “reed” and accurately describes the sturdy stems
that bear big, paddle-shaped leaves and flamboyant, gladiolus-like flowers in
sunset hues of yellow (like ‘Caballero’, left), gold, peach, orange, scarlet,
red, rose-pink and cream.
Gardeners in cold climates can now find a wide selection of packaged canna rhizomes in early spring at garden centers or bulb dealers. The rhizomes can be started in peat pots indoors under lights around early May to plant out in June when night temperatures exceed 13C (55 F). Or, you can do as I did and buy a potted plant later in the season. Canna rhizomes should be planted in rich, moist soil that’s been liberally amended with composted cattle or sheep manure or your own compost. (If you’re starting them indoors, begin in a soilless potting mix to prevent soil-borne disease and insect pests.) The rhizome should be positioned so there is a ½-inch layer of soil above the growing “eye”. Don’t water them too much until growth starts, then increase the water. In fact, since all cannas are more or less marginal aquatic plants in their native habitats (one species is Canna aquatica) and quite happy growing in boggy soil, you can’t really overwater them.
Feed them every two-to-three
weeks with whatever balanced fertilizer you use for your annuals. They need
full sun to flower well and will send up new flower stalks over a long season.
Depending on the cultivar, they reach heights of two-to-four feet (e.g.
Tropical 
Rose,
Caballero, above, and Pfitzer’s Chinese Coral) to six feet for Pretoria or the
Bengal Tiger Canna, an old favourite with orange flowers and stunning,
green-and-yellow-striped leaves. One of
the best collections of canna lilies in Canada is featured at the Montreal
Botanic Garden. They are contained in
trial beds where you can check out lots of different cultivars and make notes
of those you like.
When I was there recently, I noticed that the MBG designers had done something quite exquisite with these big tropicals. Flanking the entrance to the long, formal gardens, they’d planted lots of a particularly fetching red canna, then seeded around it masses of the wiry four-foot annual, Verbena bonariensis (shown at right). The combination of the stolid cannas with the zingy purple heads of the verbena was ingenious and it made me realize how important it is to place canna lilies very carefully in the garden.
I certainly wouldn’t recommend lining them up like a regiment of soldiers as the Victorians did, but they look sensational placed as exclamation points, say in a swirling sea of big ornamental grasses. A perfect backdrop is fountain-like maiden grass (Miscanthus sinensis) ‘Gracillimus’ which grows three-to-four feet with very thin blades and is one of the best grasses. Cannas must be stored indoors for winter. Wait until frost blackens the leaves, then cut the stem to the ground, lift the rhizome and let it air-dry for a few days before storing it upside down in dry peat moss. Keep it in a cool, dry place and divide it in spring, making sure each division has at least one growing eye.
Adapted from a
column that appeared originally in the Toronto Sun