Answer: When the petals begin to fall from the sunflowers, it indicates the seedhead is ripening. Don't prune the flowers off - those are the only flowers your plant will produce. When the seeds are dry (run your hand over them; if they are loose, they're ripe), you can save them for planting next spring. Sunflowers are annual plants and will grow and flower best when temperatures are hot and days are long. I don't think you can get them to grow all year around, even in southern California. But, you can certainly try. Take a few of the seeds you saved from the original plants and plant them in the bed. If they germinate and grow, you'll have new sunflowers. If not, you've only wasted a few seeds. While you're waiting for the weather to warm up so you can grow sunflowers again, why not fill the empty spaces in the border with cool season flowers such as snapdragons, primroses or pansies?
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