@JonnaSudenius
Hi,
I believe your photos posted to Cephalaria gigantea are almost certainly actually Cephalaria alpina. (Cephalaria gigantea is truly gigantic - take a look at my photos.) I realize the internet photo record is rather mixed up between these two species.
Please let me know what you think.
Thanks,
Lori

Hi Lori,

I checked the plant, but I'm still pretty sure that mine is C. gigantea. The picture on ATP is from the young plant, so it looks smaller than it is now (over 200 cm). Besides that the plant is inbetween some strong growing plants, so it can't develop the way it should. What make me think it's indeed the C. gigantea is the color. The C. alpina is more withish than yellow.
I'm not a botanist, so I'm open for any other comments you have. Searching the internet gave me no real solution. English is not my mother language, so first I checked the Dutch pages about these plants. All the Dutch pages say the C. alpina is growing not higher than 150 cm, but some English pages speak about 250 cm. Do you know if there is a difference in the leaves? Or any other way to really identify the plant.

Kind regards,
Jonna

I have to conclude that I am probably mistaken, Jonna.
After much searching, I did find an old description of both but I don't understand how they are distinguished from it in any way that would show in the photographs. The two species come from different geographical areas but both are shown in photos from the wild as having pale yellow flowers (or more tersely in the descrption, "yellow") so I don't believe flower colour is useful.
Maybe I'm forgetting how they look when they're immature.
Anyway, please accept my apology for casting doubt on this ID.
Lori