Tom,
Fully mature canna seed can survive for an extended time providing the pathogens cannot penetrate the hard seed coat. I have seen fallow ground produce canna seedlings years after the area was devoid of cultivated cannas. I suspect the acidity of the soil ultimately breaks down the seed coat and if conditions allow, the seed will germinate. This occurrence proves to be a problem for the commercial growers because they often plant a new crop on old canna ground. The resulting seedlings, if not rogued out, will be harvested with the planted cultivar and the customer gets something not wanted.
Kent

Thanks Kent,
It has been many years since I've had cannas. In fact, I cannot even remember the variety, or even the color that I had. However, I will probably--out of curiosity--baby this seedling along to see what comes of it.
Thanks Again,
Tom