12 July 2009
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Canna

Cannas are easily grown tender perennials with architectural foliage and brash flowers that inject a dash of exotica. They can be grown in large containers or as focal points in sub-tropical schemes. They add shape and colour to the end of the summer season.

Recommended varieties

The most popular kinds of canna tend to have gladiolus-like flowers perched high above the large, paddle-like leaves. In addition to those listed below, keep an eye out for new hybrids that keep coming on the market. Cannas generally grow 1.5m to 2m (5ft to 6ft) high, with a spread of nearly 60cm (2ft).

C. 'Black Knight': has bronze leaves and deep, dark red flowers, which add a stylish touch.
C. indica 'Purpurea': the dark purple leaves are set off by the bright red (sometimes orange) flowers.
C. 'Lucifer': a good choice for smaller gardens or beds because it grows just 60cm (2ft) high, and has red and yellow flowers with bright green leaves.
C. 'Musifolia': the biggest canna with huge, dark green leaves with red veins and red stems. It hasn't been known to flower in this country so it's best grown for its foliage. The Royal Horticultural Society has given it its Award of Garden Merit (AGM).
C. 'Richard Wallace' (still known as 'King Midas'): the dark green leaves make a dashing contrast with the bright yellow flowers.
C. 'Striata': the leaves are light green with a yellow tinge, and have marked bright yellow stripes or veins. They are topped by orange flowers. The Royal Horticultural Society has given it its AGM.
C. 'Wyoming': its huge, purple-veined leaves make an immediate impact, while the flowers are warm apricot-orange. The Royal Horticultural Society has given it its AGM.

Water cannas

These can be grown as marginal aquatics in plastic baskets around the edges of a pond. In the west of England they often survive in ponds all year, but in colder parts of Britain they need to be removed in winter and protected from frost, as with border cannas.

C.'Endeavour': has raspberry-red flowers.
C. 'Erebus': pale salmon flowers. The Royal Horticultural Society has given it its prestigious Award of Garden Merit (AGM).
C. 'Ra': lemon-yellow flowers. The Royal Horticultural Society has given it its prestigious Award of Garden Merit (AGM).
C. 'Taney': apricot-orange flowers.

Growing tips

Site and soil preferences

Cannas like rich, fertile soil and wall-to-wall sun.

Planting associations

Cannas often look good when grown in contemporary gardens with stone and decking.

The purple-leaved varieties associate well with silver-leaved plants. They also contrast brilliantly with the orange flowers of rudbeckias or the vivid spikes of kniphofias, more familiarly known as red-hot pokers. Also try them with the cerise blooms of Lychnis coronaria or the bronze leaves of scarlet dahlias, such as 'Bishop of Llandaff'.

In small gardens, grow cannas in containers but ensure you pot them on regularly so they're never short of moisture and nourishment.

Watering and deadheading

They need copious drinks through summer, especially in prolonged dry spells. Apart from that, give a monthly feed and deadhead as necessary.

Winter protection

Come the autumn frosts, cut off the foliage and dig up the rhizomes, cleaning off the soil. Store them in dry, soilless compost in large pots in a frost-proof place (for example, a garage). They can be started into growth again in March.

Propagation

In spring, when repotting, see if a rhizome has several eyes or new young shoots; if so, slice it up so each piece has an eye and set of roots. Put each in a pot filled with multi-purpose compost and stand in the warmth.

Water gently at first, then increasingly as growth begins. Don't plant until after the last of the frosts.

You can also grow good-sized plants from seed to flowering in one season. The seeds are black, about the size of a small pea, and very hard. Soak them overnight before using. Sow in a small pot of soilless seed compost and put in a propagator heated to about 23°C (73°F). They should come up after a few weeks. Once this happens, pot them up and grow them on.