Hola!
Greenskell just tagged me here, so I'll add a few thoughts.
As he said, I'm in a sub-tropical area, around 22N.
I've got some experience growing indoors under lights,
and now outdoors guerilla style in the sub-tropics.
I see you've been doing some study / reading, which is awesome!
But, remember that most stuff on the internet
is for people in Europe or North America, different climate from you and me.
For germinating the seeds, I'd suggest first soaking for maybe 12-24 hours,
and then either planting directly into soil
in small pots,
or using the "paper towel" method for another 24+ hrs until seed sprouts.
Soaking for 10-20
minutes won't do much at all.
You can look up soaking and paper towel method online, or better yet, here at AFN.
Just putting the seed into the soil without prep may actually lead to more chance of problems.
I
would not plant directly outside.
As mentioned above, I have found that starting in a 1 Liter pot works great.
Sprout it indoors in the pot, by a sunny window or under little lights (like CFL flouro).
A 1L pot will be enough for the first 2-3 weeks of life.
This is important, as you can then really look after the young seedling.
Avoid big changes in temps (you prob don't have that prob in tropics, though),
and maintain soil moisture levels well, i.e. neither too wet nor too dry.
Use the best potting mix you can.
A little perlite is nice, but ... maybe just 10%-20%, I wouldn't go to 30%.
But: make sure you check a couple of things on the potting mix:
What is the pH? Try to get pH around 5.8 to 6.5. No more, no less.
And for NPK (Nitrogen, Phosphorus, Potassium), go with about 1-0.5-0.5.
Do not use something that has slow release fert in it already.
If the potting mix bag doesn't have any pH and NPK figures, don't buy it.
Otherwise, sounds ok. Similar to what they sell here.
(Though my pref is some imported brands, mainly German....)
Prob no need to add anything of your own.
If it's your first try, don't go mixing stuff up.
Just regular standard potting mix or seed raising mix. Perfect.
If you use the soak and / or paper towel method,
make sure you prepare your pots maybe 24 hrs before hand.
That includes getting the soil nice and wet, but a little time to drain.
Once the seed is sprouted, make a little hole about 1cm deep in the top of the soil,
and
carefully (may want to gently use tweezers) to put the seed sprout in.
If you can (but don't worry about it too much), have the sprout tip pointing down.
Then very gently cover over the seed, add a few drops of water.
Do not press the soil over it.
Whether or not you need to cover with plastic film?
Depends on your local humidity and temperature.
Since you're tropical, prob the temperature is perfect.
You want relative humidity RH about 70-80% for the sprout / seedling.
If that's what your local RH is, no need for the cover.
(I don't use a cover, and my local RH is about 70-80%.)
Too wet is not good, can cause fungus and "damping off",
or make the seedling grow very tall and skinny, which will fall over...
If all goes well, and it most likely will,
the seed will pop from the surface in about 2-7 days.
How much water to give it?
Again, depends on local humidity.
If you're quite humid / wet, then if the soil is soaked when the seed goes in,
may not need any water for the first few days.
If the surface of the soil is wet / damp, don't water it!
Over-watering is the most common beginner mistake.
But don't let it dry out either. Dry sprout is dead sprout.
Check it once a day, you'll be okay.
As above, do all this in maybe a 1L pot to start with,
for first 2-3 weeks of life of the seedling.
If you local soil is really top quality, you prob don't need much nutes.
But, probably you do need some.
Or, rather, you don't
need it, but it will help and give a better result.
Epsom salts / mag sulph is good for magnesium, but it's not the main thing.
The main thing that the plants need is Nitrogen, Phosphorus, and Potassium - NPK.
And secondary nutrients, most important Calcium and Magnesium, then prob Iron. Ca Mg Fe.
What nutrients a plant needs changes during growth stage.
At first, a little more N as it builds up leaves and stems.
Something like 5-2-2 NPK, or similar ratio.
(Ratio most important, as can mix stronger or weaker...)
But into flowering, more like 2-5-5 NPK or something.
As for Ca and Mg, depends:
If you use tap water, and it's hard water = high Ca,
then prob not much need so supplement.
But if you use purified / RO water, then it's soft, low Ca.
You may need some nice Ca / Mg booster, like Epsom salts / lime.
If you have a few $$, there are some great commercial products.
Check out some of these:
http://www.autoflower.org/threads/n...r-packs-kits-info-and-links-2016-09-24.55182/
They're mainly designed for growing our kind of herb. ;-)
During first couple of weeks, the plant is vegetating, growing green.
Most good potting mix will be enough nutes.
But in flowering, once the flowers start to show until the harvest,
then the soil's nutrients may be used up already,
and only then need nutrients.
So one simple option is to just buy a "bloom" / "flowering" fert,
and only start to use it once your plant is flowering.
Most autos are bred for 20/4 or 24/0 light cycles.
But don't worry. Some of us growing outside in tropics,
just use natural 12/12, and they do just fine.
Canna is "heliophilic", meaning "loves the sun".
The best is full sun, as much as possible.
Unless your midday sun is maybe over 35 C hot,
in which case, may slow down or get a bit too hot.
Choose your strain to grow well,
can find a strain that likes the heat.
After doing 2-3 weeks inside / window then transplant out.
Transplanting is pretty easy, just look it up how to do it.
Give it the sunniest spot you can find, for your security situation.
More sun. They like the sun. Need the sun.
Not the heat, but the light.
Sun. Lots of light means happy plant.
If you can't get all day sun, usually morning better than evening.
(Sky is clearer, less human pollution...)
You've come to the right place.
Happy growing!