Rewilding My Lot

This conjoined flower caught my eye, and of course I had questions. Is this common? What causes it?

First, the plant is a volunteer sunflower, I believe perhaps a Cucumberleaf Sunflower (Helianthus debilis). I have several of them here, and they grow to about 3-4 feet tall. They are also called Beach Sunflowers, and although I am definitely not in a coastal area, I do have sandy soil.

Here’s a photo of a normal flower head on this plant.

There is a relatively rare phenomenon called fasciation, where plant parts grow abnormally to become elongated or fused together, so the conjoining of flowers is possibly what is happening here. The cause might be a hormonal imbalance or genetic mutation. Another explanation for a double flower is fertilization of two of the flower’s ovaries instead of the usual one. I don’t know enough botany to tell exactly what’s going on, so I will just celebrate this double flower as a quirk of nature. It’s the only one that I have noticed here so far.

Here are more photos of the conjoined flower heads.