Cannas Flower Bulbs
Cannas are superb summer bloomers because they can either be grown in containers or in the open garden. Between the textured and often coloured leaves and the exotic flowers, they make a lot of show for very little effort. While they often bloom for most of the year in their native tropics, winter (the great leveler) will not allow them to do so in North America (well, maybe in zone 9 and 10 they can be left outdoors all winter).
How to Grow
The canna bulb is native to southern areas (West Indies and South America) so are considered tropical plants and definitely not hardy.
This means they grow best in full sun, with adequate moisture and should not be planted outdoors until all danger of frost has disappeared.
Plant the rhizomes horizontally four to six inches deep and space each cannas flower eighteen to twenty four inches apart.
Because the leaves are half the show, do not plant in windy spots if possible or the leaves will be blown around and be damaged. A little protection will give superior results for both the leaves and their ability to stand upright.
The dwarf canna plants generally reach two feet in height while there are some varieties and species (C. iridiflora) that reach 9 to 10 feet tall. Our garden plants come from breeding of C. x generalis the Canna lily. And there are quite a few varieties now both in flower colour and leaf colour.
And as a note, they are superb as pond side plants because they handle damp soils very well.
Propagation is either by dividing the rhizome in early spring before planting or by seed. If you collect seed in the fall (not too likely in northern areas but possible) you can soak it for 24 hours in warm water and then sow. Keep the seed at 70F until germination occurs then grow on under full lights at 62F.
Canna 'Chinese Coral'
In the fall, allow the bulbs to get hit by frost (or harvest right before frost) and the stems blacken. Dig up the rhizomes and allow them to dry outdoors for a day or three until the soil left on the rhizome is dried out. Store dry in wood shavings or vermiculite in a cool dark location.
If you want early flowers
In the spring (divide if necessary) pot up the cannas and grow under full grow lights at a warm temperature (80F is ideal) Be careful when handling or potting because the roots can be quite brittle and tender. If the rhizome sends multiple shoots, your choice is multiple shoots and small flowers or pick the largest shoot, cut off the rest and have the biggest flower. You cant do both. It is either several smaller flowers or a single big flower. As the rhizome is growing, feed the flower bulbs weekly with a balanced liquid plant food to keep them growing strongly.
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