I'm a zone colder than you. I usually plant mine about end of 2nd week to 3rd week in May & usually deep enough so they don't sprout until early June. Since you're in a warmer zone it'd be depending when your last frost hits your area...otherwise, if they come up and we have frosts they'll freeze off the plants as tropicals require warm weather unless you cover them. With 4" of SNOW on the ground here just yesterday a.m. certainly no rush.

Ann, Plant your canna in nursery pots now to get a jump on the season. Dampen your potting soil and place tubers in pots. You don't need much water at first because it will make them rot. You don't even need sun or lamps until the tops sprout. That takes about 2 weeks. You can transplant these into your garden or place them in planters. Can't help you with dahlia. Good luck. Billie