Unfortunately I did not find your original thread so we are lacking any additional information you might have included.
If you had sound healthy cannas when you planted three weeks ago you should be seeing sprouts emerge by this time of year. You very likely should have seen some bud swelling on the rhizomes even when you planted if they were sound. At this time your only option may be to dig into the container and check the rhizomes for growth. I am assuming they were not planted more than two to three inches below the soil line. Might be interested to know when you received your cannas and were they stored in a frost proof area prior to planting?

Kent

I bought the canna's together with a few dahlias around mid april and immediately immersed them in sphagnum moss, put everything in a large styrofoam box with lid and kept them in an outdoor shed. I checked them every 2 weeks and the dahlias started to sprout so I got them in their pots and they are now well on their way. The canna's showed no sign of sprouting so I left them. I waited until night time temps reached 50 and planted on May 24th. They were healthy and firm but no sprouts. I did plant them deeper than you said, maybe around 6 inches.

Hopefully the planting depth accounts for the delayed emergence. If possible, you might scratch down and check for growth. They were definitely planted much too deep. Unfortunately deeply planted cannas can tax long term stored rhizomes to the point that they do not have enough stored nutrients to produce adequate growth for emergence.

Let us know what you find.

Kent

Thank you, It has rained for a few days and as soon as the surface of the pots dry out I will do as you say and dig down a little. Sadly of all the plants I bought from this grower the canna's were what I wanted most. I will let you know.

Susan

Hi Kent,

I did as you said and dug into the container. Actually i took the annuals out and was surprised at how far down the Canna's were. Thankfully they were fine with juicy, plump white shoots. I reseated the Canna's at 3-4 inches down and replaced the annuals. I have 2 large containers planted with Canna's. I left the other one alone with the Canna's down around 6-8 inches.
Thanks so much for your advice.

Susan

Hello Kent, I had to laugh today as I passed the container that I did not disturb, I saw 2, 2" shoots. That will teach me to leave things alone. Thank you for your advice, I will feel more confident with this plant for next year.

Susan