Sonatta at 20 to 24" is a short variety of Cosmos, but not 3 inches. The taller ones are 3 or 4 feet tall. It is a full sun plant and shouldn't be planted in the shade.

When you dug them up was the root still in that same little ball? It sounds to me that your cosmos was pot bound when you planted them, and if they were still in that same ball it confirms it.

When a plant is in a small container for a long time the roots have nowhere to go so they go round and round in the bottom of the container. If you don't loosen them so they are hanging down they will continue to keep going round in the same way. The plant can't get what it needs to grow.

Dig them up and loosen the bottom roots. Then give them a gentle squeeze from side to side and replant. You should always look at the roots of any plant before you stick them in the ground.

As for deadheadding--The purpose of deadheadding is to remove the spent flower so it doesn't go to seed and so your flower will keep putting out more blooms. You just remove the flower. If you cut back to the stem you will be cutting off potential side shoots and have a mighty skinny plant with few flowers.

They've been known to sulk planted as transplants. There isn't anything much easier than cosmos planted by seed. You might consider giving that a whirl sometime.

Tks to both ! As far as rootbound, no...that wasn't the problem. In fact, they didn't have much of a root system to begin with, with the dirt falling off when removing them from the little pot. I think they weren't mature enough to be sold, now that you mention that.

Oilpainter - TKS for explaining that about deadheading !! I have never been sure and would have cut it down to the main stem.

Another question to you (or anyone) - I've always harvested seeds at the end of the year but I can save those dead flowers for seeds NOW, can't I? And can I toss them back in the ground now too?

Calliope, I think you hit the nail on the head, esp. now that I've seen the pathetic root system. I have some seeds...will just throw them down in same area.

No you can't save those dead flowers--well you can but there is no seed in them. In order to make seed the seed pods have to stay on the plant and ripen. If you do that now you cut down flower production. Deadhead all summer and stop about a month before frost. Let the seed heads mature and ripen and when they are brown and ready to drop their seed then collect them.

Having said that--you probably won't get the same flower or plant next year. Sonata is a hybrid and will in all likelyhood not come true. In order to get the same plant they have to be hand pollinated with like plants and then sealed in a net bag so no other pollinator can come near it. The seed is then collected and sold.

Cosmos is not an expensive seed--I'd buy some if you want the same plant.

My Sensation Cosmos were started from seed in a seed pan and then transplanted to one gallon pots. I have about twenth of these pots growing in strong sunlight and they are growing strong. I have cut them and pinched them back to stay under fifteen inches tall, waiting for blooms to start because I want to bunch them by color when I palnt then in the garden.
The Problem is there are no blooms, not even one! I rread t hat Cosmos need to be watrerered spariongly or they won't bloom and I have tried that for the last three weeks, to no avail. These potted plants are now about ten weeks old.
Help Please!

Cosmos thrive in "lean" soils. If the soil has been enriched with fertilizing and the plants are given too much water, they don't do so well. They do, however, start to bloom more heavily as the days get shorter.

Maybe this is a strange year; my 4-packs from a garden center were supposed to be the tall Sonatas. They're blooming heavily, but maybe only 18" tall.

Michael, if you stop pinching them, they might flower.