Found a good way to grow canna from seed
I found this at some other site, and found that using this method I had about 95% germination. Thought it might help someone to post it so here it is:
Canna hybrids do not come true from seed and although some of the progeny may resemble the parents, they are rarely as good. Nevertheless, it is fun to grow a few this way and you never know, you might just get something that is even better. The best time to sow is in January or early February , which will give the plants a good 14 - 16 weeks growing time before they can be hardened off for planting out of doors. Thankfully Cannas are extremely easy to grow from seed if you observe a few easily followed rules.
The seed coats are bullet hard (hence the occasional common name of 'Indian Shot'). The best way of enabling water to penetrate this seemingly impermeable barrier is to nick the seeds, by holding them in a pair of pliers and using a file, carefully cutting into the coat until you reach the white endocarp within the seed. Only the tiniest amount needs to be exposed and it is better to file too little away than too much. If you look at the seed carefully, you will see a scar (hylem). It is through here that the growing shoot will break through. You should file the coat on the opposite side to the scar in order to avoid damage to the embryo.
The next step requires a bit of bravery, so you'll need to 'grit yer teeth'. Place the seeds in a cup or beaker and pour freshly boiled water over them. As soon as you hear the seed coats starting to crackle and pop, immediately add enough cold water to cool them down to luke warm. The seeds should then be allowed to soak for 24 or more hours in a warm place - an airing cupboard is ideal.
Inspect the seeds and most should have swollen to almost double their original size after 24 hours. Sow these just below the surface of lightly moist, sterilised, soil-less compost and maintain temperatures of 25C (77F) or higher. Germination will take no more than 48-60 hours and don't be surprised to see first shoots appearing in as little as 24 hours. Those seeds which have not swollen immediately, can be left to soak for another day or so before sowing.
In the early stages, seedlings need to be kept at around 21C to prevent damping off. Canna seedlings need lots of light and should be left to grow to the second leaf stage before potting up into 8 - 10cm, diameter pots. Once they have established well, temperatures can be gradually reduced to 15 -18C. Pot on as necessary and keep the young plants moving by applying half strength liquid feed at 14 day intervals. By May, the seedlings should be in 25 -30 cm. diameter pots and will be ready for hardening off for planting out in the first week of June.
If you start early enough in the year and maintain good growing conditions, you can expect first flowers by July or early August.