Collard Greens

I planted my collard greens last year (one plant) and we had a great supply coming in from October-February-ish. As the heat started (I live in So. Cal, Zone 9) the plant stopped producing the big leaves and would only put out tiny leaves that you couldn't do anything with. Then it flowered and those grew out of control.
On another site I was told to cut all the flowers off the plant, as once it flowers, it will not produce again. I did this and now my plant is bare, with a thick, healthy looking main stem, but no new leaves. I sure hope my cutting the flowers off was the right thing to do, but now I'm not so sure!
I hate the thought of pulling it up, as the stem itself looks so great. Thick and green, but the leaves coming up are still so small. It has been VERY hot here for over a month, but I was wondering if collards reproduce each year, or do they need to be pulled up and new seeds laid down every year?
I hope this made sense; I am a gardening novice! Thanks for any advice on this great plant!