Buddlea

Definitely try cuttings as it's a particular colour you are after. We have 5 self sown buddlea and I am trying to kill 4 of them.
They grow so rapidly and self sow all over the county.

We had one growing out of the top of our chimney, it grew despite fumes from the boiler.

Several cuttings growing in pots at the moment as we have cleared some trees, but I bet that the one colour I want to root( deep purple) , won’t.

Our neighbour has one growing out of a joint in her garden wall. I suspect a seed was blown across the road from a neighbour's garden.
I grew one from a cutting very easily when we had an allotment and I wanted to attract butterflies.

sharp drainage...

If you have the original plant I'd suggest sprinkling some seeds on a seed tray with a layer of gravel over the compost, too. It grows from seed extremely easily, especially with very shard drainage.

Cuttings should be semi-ripe. I think they should take at this time of year.

I once tried to buy buddleia plants from a garden centre in Fife. Asked the owner if he had any because I couldn't see any among the plants for sale. He laughed like a drain and then went and dug me up some of the thousands of seedlings in his car park!

I saw one growing out of an first floor window sill. You have to hand it to buddleas, they are indestructible.

Same as J52.
I was walking today in a very urban area (NE) and saw young buddlea seedlings sprouting in cracks in concrete and between small paving stones.
It's a vigorous plant and soon takes over.

The seeds from the parent plant appear easily. Unless the parent plant is elsewhere.

You have two chances as my friend always says. I'd be surprised if it didn't strike as buddleia seems to grow very easily in all sorts of situations so give it a go.