Sorry this isn't a reply to your question but the yarrow you mentioned might be one I've ben looking for. I have an off white that is very long blooming and looks wonderfull in the evening or at night when lights hit it-great for a 'Moon Garden". I'm not sure if I have the right name but I've been looking for what I thought was Athena whenever I see an off white for sale. No luck yet. Could you tell me if Anthea behave like I'm looking for? Having the right name will surely help.

What you're describing sounds very pretty but I don't think it would be Anthea based on your description. Anthea is definitely yellow but a paler yellow than 'Moonshine'. Sorry I'm not much help. Is the foliage on your plant fuzzy grey or is it more of a very ferny green foliage? That might help some other folks with the identification.

Kim