I live in North Queensland Australia.
There's a secret to cooking Queensland Arrowroot (Canna Edulis) so it tastes good.
Arrowroot has a compound in it called the F**k.
Basically you have to cook that compound out of it to give it a delicious potato type taste.
In other words you have to cook the F**k out of it.
My best success cooking arrowroot has been leaving it in a
solar cooker on a sunny day basically from 11am to 4pm or later.
Then it tastes fantastic.
Also some of the tubers can get huge and alien looking. Generally speaking you want younger tubers than that...still fairly clean looking like a large ginger (kind of).
And here in the tropics I don't know of anyone growing arrowroot from seeds. We just break up the tubers and replant them.
Keep them watered or better still, plant them in the wet season and just let them go.
It's a ridiculously easy plant to grow in the tropics. We use it as a border plant to suppress weeds and cut the tops off regularly to use as mulch.
Having said all that we don't eat them very often. There are simply better, more nutritious options like sweet potato, taro and yams.