Hi. I started my canna rhizomes off in pots in my unheated greenhouse a couple of months ago. Some of them still haven't sprouted. I wonder if I planted them too deeply; I was assuming that, because the instructions say to plant them at a depth of about 6 inches, I should plant them at that depth in the pots. Maybe I needn't have done so? Could that be what is delaying their growth, do you think, or are the rhizomes not viable?

Is it worth scraping some of the compost (dirt) off the non-sprouting ones?

Thanks for any advice.