Is there a feminine form to the name Clayton/Clay?
Calathea -- "kah-LAY-thee-uh"
Not one that I’m familiar with. There’s a trend of using traditional boy names for girls so you could try just Clay or maybe Claye as a different spelling. It could be a middle name. Clayne is another option that sounds a little more feminine. For Clayton you could go for something like Leighton which is similar.