Monday, July 21, 2008

Creating cannas for the ever-flowering tropical garden

The creation of new flowers is something most gardeners leave to professional plant breeders. Since there are very few professional plant breeders in the humid tropics, the rate of development of new varieties in the humid tropics is very slow. I would like to change this by getting more gardeners into plant breeding, starting with something really easy -- tropical cannas.

Cannas are good subjects because they come in many different floral colours including red, yellow, orange, pink, cream, near-white and mixed or mottled. The leaves are green, red, or striped. There are talls, mediums and dwarfs. Each flower lasts usually two days but a head of flowers may carry up to 20 flowers. An inflorescence usually bears 2-3 heads of flowers in succession and some bear up to 15heads. For every shoot in flower, another should be half-way and a third pushing up from the rhizome underground. Flowering can be prolonged for years.

Here are some other statistics.
Time from pollination to seed-ripening: about 20 days
Time for treated seeds to germinate: about 7 days
Time from germination to flowering: about 3 months
Time for doubling of plants by division of rhizomes: any time after 4th month

There are few plants that one can hybridize and evaluate within 6 months. This is a phenomenally rapid rate compared to tulips, curcumas and orchids.

As far as I know, all cannas, if fertile, will hybridize with each other. However, many garden forms are sterile. The fertile ones advertise themselves by producing fruits spontaneously and spradically. To start your breeding programme, make a collection of fertile varieties first.

To produce new hybrids, apply pollen from a fertile plant to the stigma of another fertile plant. This is best done in the afternoon, using freshly shed pollen.

Open a fully developed bud (tomorrow's flower). Strip off the sepals and petals until you are left with the two innermost members. One will be a stamen, somewhat like a small petal in appearance, which bears an anther on one side. The other will be a flattened pistil, at the tip of which is the stigma. The anther will already have split and deposited its pollen on to the side of the pistil. The pistil, with the pollen on its side, can then be used to dab the freshly shed pollen on to the stigmas of already opened flowers.

After about 20 days the seed will ripen. The seeds harden on drying and will keep for a year or more. To germinate, make a small cut in the hard seed coat with a wire cutter and plant about 1 cm deep in soil.

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