Removing your entire underground rhizomes is not difficult but does require a little effort. Loosen the soil completely around and under the plant. Use the foliage to pull the entire plant out of the bed. I find using a heavy digging fork works better than a shovel. Your soil makeup will determine the amount of effort required.

Your stem containing the seed capsules have likely not matured to the point of maturity needed to harvest viable seed. You may wish to revisit the reason for the earlier recommendation. I am guessing that these pictured seed capsules needed another 5 to 10 days to mature before removing. The capsules typically will become somewhat dry and turn brown before you can harvest mature seed. Sorry for the misunderstanding.

Kent

"Also I am including a macro photo of a cluster of blooms that someone here told me to cut off. "

Hi again, are you referring to this discussion? There's nothing said there about saving seeds as a goal of yours.

Agree, those are not yet ripe. That's why I said: "The flower stalk can be removed at this point, so the plant doesn't put any effort into ripening those seed pods." This does not say to cut it or not cut it, just that it can be cut if the desire is for more flowers to form instead of waiting for the seeds to ripen.

Is your diseased plant in the ground or a pot?

The lines and circles were drawn for another purpose, but these are Canna rhizomes I dug up recently. If in the ground, you may want to wait a few weeks after excavation before planting anything else, just to make sure you got them all. If you didn't, you'll soon see new foliage coming up. Within a year, the amount shown in the pic can make enough new rhizome material to fill a 5-gallon bucket. Some of it can be quite deep in the ground.

Sorry for the misunderstanding...mea culpa...No, I am not interested in seeds at all. Yes, its in the ground, the healthier one is in a pot. I suspect that whatever is eating the one in the soil is a plant of my neighbor that is actually hovering and touching the eaten plant. But her plant looks healthy so i do not know if that is the cause.for sure. All I know, other plants in that spot have had no problems in the past, such as this one. Yes, new blooms have appeared on the one that i cut off.

Not a problem - smiles! Being eaten is not a disease. Is your neighbor's plant also a Canna? Lots of things that fly like to eat Canna leaves in passing, but there are canna leaf roller caterpillars in particular that (you guessed it) live in the rolled leaves. They don't actually roll them, but do seal them shut with webbing so they stay dark and moist inside. Then they eat the tender new growth, preferably the flower buds, before you ever even see them. Does that sound like what's going on? They are a huge problem here, requiring daily maintenance. I don't know how far north the problem extends, probably the same as the range of the Cannas.