The Butterfly bush-Buddleja is not native to Europe, that's why we treasure them so much.
From the 100 species in the genus Buddleja the most popular is Buddleja davidii from central China.
Buddleja davidii, also called summer lilac or orange eye is naturalized in most central and southern Europe. It is much appreciated and used as an ornamental plant in butterfly gardens and parks.
The lilac to purple inflorescence is produced in panicles at the end of the arching branches and often are honey-scented.
The flowers are what they call the "perfect flower" meaning that male and female organs are found in different flowers on the same plant and they are often wind pollinated. Though they don't rely on winged pollinators, the flowers are an important nectar source for many species of butterflies, bees and hummingbirds.
Here is a pink butterfly bush flower with a Red Admiral butterfly gathering pollen.
Red Admiral butterflies have a fantastic, vivid coloration on the upper part of their wings. Unfortunately, from my position and taking care not to shake the bush, I could capture most of its underpart, which is dark, marveled.
Here is a better view of the Red Admiral butterfly's coloration.
Though Wikipedia says that this species of butterfly bush is not able to survive by temperatures below about -15°C to -20°C, our bushes are adapted to much lower temperatures during our cold winter days.