Amaranthine: Unfading, everlasting, particularly in relation to a flower. From the Greek amarantos, undying, and anthos, flower.
Amaranth is the name given to a genus of summer flowering plants, most of which go by the (very) common name of pigweed. Now, there’s a step down for you.
It’s also the name of a purplish-red colour and a synthetic red food colouring ( E123), used in packet soups, cakemixes, etc.
Why do I love it? Well, I’m a sucker for a word with overtones of colour and I think I conflate the purplishness of this word with amethyst, which gives amaranthine a jewel-like quality in my mind. I also like the association this word has with the concept of a magical, undying flower.