Unless you consider them very unsightly right now, there's no reason not to let them stay green as long as possible. You can cut them back after they have frozen and died, or even cut them back in spring. They will naturally die down all the way to the ground when they do go dormant. The stems should basically fall out on their own or you can cut them down to 1-2 inches. They may be established well enough survive winter whether you cut them or not, but you'll certainly improve your chances even more if you leave them green as long as possible. September-planted mums sometimes make it and sometimes they don't. But the green leaves will allow the roots to continue getting deeper.

scott - Crotons will not form roots when the overnight temperature drops below 65 degrees F. For optimum success, you really need the nighttime temperature to stay above 70 degrees F. I run a mistbed from April through September each year and grow cuttings of around 300 different varieties. Every time I've pushed the envelope and started early, I ended up throwing a bunch of rotten sticks in the trash.

I usually cut them back in my garden, so the plant spends energy making more flowers rather than trying to produce seed. Are there other people in your area that can get hummingbirds to stay? It seems to me they would have to answer their migratory call and move on. I know when I lived in CA I had hummers 9 months out of the year, but they always disappeared for three months. Now I know how spoiled I was to have them as long gas I did!

debndulcy, The best thing you can do is just be patient. It's going to take a few years before your new plants will take off. You have to consider that you've just taken away your plants access to nutrients and it has to start all over just like a seed would. Look at how many roots are on the plants you buy, this doesn't happen overnight it takes a long time and a lot of man hours to get those plants looking that good.Then look at how few roots are on your cuttings. You've already done the hard part now just take good care of them for about 2 or 3 years they will be fine. Regular fertilizing and watering is the fastest way along with long hours of light. Long hours under lights will make the difference I'm sure. I have some hydrangea cuttings that I've been nursing for 2 years and they may finally be able to be put in the ground next year. I hope. I just stuck some mum cuttings about 3 or 4 weeks ago and still have my fingers crossed. Anyway Good Luck and just have fun with it.