I bet you're right. In poetry, primroses are always pale yellow. Cultivated, they're available in nearly every color of the rainbow. I had no idea they could self-seed and naturalize... but plants probably behave differently in places like Europe where it actually rains more than twice a year. 
Now that I thought about it I think these are hybrides too which only in colour resemble their wild ancestor.
And you are right, they like slightly damp shaded soil. Which plants grow wild in your gardens? Or has everything to be planted?
Those are pretty. Are they hard to grow?
No, I think not. I never care for them in my garden and they just seed themselves. They use to be popular pot-plants in spring too.
Outlawing it might be typically German (though I still wouldn't want to bet on that), but unsurprisingly, lakes elsewhere are no less prone to having their ecosystem wiped out by the excess nutrients.
The Landesbund für Vogelschutz in Bayern e.V. says one piece of bread per grandmother and grandchild is okay
if they don´t throw it in the water
