Hello Daffnet, Niels,
Took this photo yesterday, Near water on a dry spot where it has been for years now. Maybe Niels has problem with fungus due to the cold and wet spring. Could you send a picture of your plants?
Obvallaris is one of the best naturalizing daffodils in western Europe, you can ask the people in Wales.
Best regards, Hein Meeuwissen, Voorhout, Holland