Gerrit, that's a very fine looking Epi, and amusing too with the indefinitely shaped spurs. And so floriferous! What is your source for that plant? I'm wondering if it might be a hybrid with ecalcaratum, because that feature, of variable vestigial to partly developed spurs, is a strong and unique characteristic of ecalcaratum. It's hybrids, such as 'Lemon Zest' that I showed earlier, and 'Buttered Popcorn', another Darrell Probst hybrid just coming into bloom now, both show that same characteristic.
You are definitely right, determining it as a hybrid between E. davidii and E. ecalcaratum. Certainly after seeing E. 'Lemon Zest'.
KVP selled it as a davidii. I asked him about this aberration (defect) but he was not so amused. It could happen was his reply. But I was happy enough. A normal davidii is a common plant. This one is so cute.
Each individual flower is different. Sometimes 4 petals but also 3, 2 or one. Or none with only a sort of shoulder where the spur should be. It's curious and funny.
In attachment, Epimedium 'Egret'. From a Belgian source. And new to me. lovely enough.