Cannas can add new dimension to flower gardens

Published: Sunday, July 8 2012 2:53 p.m. MDT

Cannas Maroon

larry sagers

Cannas are one of my favorite summer bulbs. The most compelling reason to grow cannas is for the exotic tropical looking leaves. Few plants rival the cannas' striking foliage that comes in rich shades of red and green, maroon and bronze as well as numerous variegated patterns. They grow broad, flat, alternating leaves that grow out of the stem in a long narrow roll and then unfurl.

The plants have many wonderful characteristics. These include interesting flowers that come in several colors ranging from dark red to light green. They grow quickly and are wonderful as backgrounds for bedding plants and other garden selections. Consider combining them with castor beans, caladiums or other large leafed plants.

Although they are often called canna lilies, they are not true lilies. They are related to gingers and bananas. Canna is the only genus in the family Cannaceae. Interestingly enough, cannas are a very rich starch source and are an important agricultural plant in some areas of the world.

The plants are tropical in origin but they grow well during the summer throughout Utah. Their name comes from the Celtic word for a cane or reed.

Cannas became very popular in Victorian times as garden plants. All cannas were once native to the Americas from South Carolina around to southern Texas and then south to Argentina. Some cannas likely came to Europe via India and Africa.

Some canna cultivars are large and need plenty of room, while others are more compact and better adapted for smaller growing areas. Garden cultivars usually range in height from 24 to 60 inches but some species will reach 10 feet. They make a good background or even a temporary screen in the garden beds.

Cannas thrive in warm, sunny locations. They will thrive with the same conditions as corn — warm, well-drained soil with plenty of decayed organic matter. They are tender, so they cannot be planted until danger of frost is past and the soil is warm. Protect them from high winds as the leaves are easily shredded.

The plants are readily available from nurseries but many gardeners save their own from year to year. Planting them directly into the soil is the easiest method, but since they take longer to develop, starting them inside in pots gets a jump on the gardening season.

Most gardeners start with part of an old tuber containing several strong buds. These can be divided to single buds — but weak buds make weak plants. For large vigorous plants, use large clusters of rhizomes.

Cannas grow from these swollen stems that are correctly called rhizomes. The plants spread as these rhizomes grow so a plant can triple in size or even grow much larger over the course of the summer. Larger plants need 18-36 inches between them for growing room.

Cannas plants are not very fussy and will grow with little care. If you are looking for maximum growth, give them plenty of nutrients and moisture. They will grow as pond plants in one inch or more of standing water, but they grow equally well in a terrestrial environment in soil.

The abundant foliage develops quickly so make regular applications of fertilizer to keep them growing well. Although they have few pests, slugs and snails will damage plants as will spider mites so watch for these pests and control them before they cause serious damage.

Cannas are usually free of diseases but occasionally they are affected by specific plant viruses. These cause spotted or streaked leaves when they first start but eventually cause stunted growth and twisted and distorted blooms and foliage. Dig and discard affected plants to prevent these diseases from spreading.

There are more than 60 cultivars available, providing a wide choice of flower colors and leaf colors, as well as different sizes for the plants. Historians think there were once hundreds of canna cultivars available but many of these are now extinct.

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