Buddleia originated in China. They are also called the butterfly bush. If you want to attract butterflies to your garden, back yard or allotment plant a Buddleia. Sedums attract them to.
The Buddleia was used to reinforce newly constructed railway embankments with their roots. I noticed a lot of them growing wild near Temple Mead train station in Bristol when I visited Dorset in 2018. Perhaps their ancestors came from bomb sites in the second world war?
I make cuttings from mine every year and you can also let the flowers go to seed and sow them next Spring. I think they like to spend time frozen in the fridge to make them jolt into life and germinate.
Here's one I planted twenty years ago:
Can you see the butterfly?