Eryngium

You can prune it, but not into the old wood, a bit like lavender.
They do not last for ever, but are really easy to take cuttings from.
Choose a non flowering stem, about 4 inches long remove all but the top leaves. Make a new cut just before the last leaf node. Pop into rooting powder and then put into a gritty compost.

I have these self seeded in a gravel area. The bees love them as you may have found out. Mine die back every year and then the next year there are hordes of little seedlings which grow and produce flowers in the same year. I wouldn’t bother with cuttings as they are incredibly prickly.

Oops not paying attention, I read it as Erysimum
Ignore me!

I was given some bee friendly coated seeds and notice that one which has come up looks something like that.

I do hope it spreads, but it is a big 'leggy', however, at the moment it's near a fence so has something to lean on.

I have one and it is taller than usual. I reckon something to do with the winter rain, then hot sun.

It will die back in the autumn and pop up again next year. It spreads quite readily.

I love the metallic blue and the bees love it.

It's in my " meadow" ie a scrappy bit of ground which has had numerous wildflower seeds scattered there, most of which failed to appear.
I just thought it was a thistle, but very pretty.

I had this plant in the garden at my other house but, as I only had a tiny little space, it very quickly became to big and invasive to keep. But now I've got a lot more space, I think it would be lovely to try another one.

It’s dark now but if I remember I’ll take a photo of mine in the morning.

Here is mine see it’s much taller than normal by about 50%

Is that what I always call Sea Holly or am I getting mixed up ?

No! That’s it’s common name. Much nicer?

https://www.gransnet.com/uploads/talk/202007/medium-905141-9e71a67d-88ba-4ca3-9db6-bd15235351d8.jpeg https://www.gransnet.com/uploads/talk/202007/medium-533459-5187dabc-12fd-41f1-bea7-2d1effe14f8f.jpeg

Oh in that case I’ve got a big clump of it too. Much taller than it is usually but just as prickly . It looks so much bluer with the sun on it but here’s mine today .

Sorry if photo is a little blurred .

Yes it looks nicer in the sun, mine was taken before the sun got onto it. Loads of bees now.

Thanks all! especially for the lovely photos. I haven't yet mastered that skill. Well my plant is surviving, only a few heads have turned blue up to now.
I'm wondering where the plants in our small front garden have come from. Foxglove buddleia sea holly etc.
We came here in summer 2018 and they weren't here then.
Last summer the sea holly appeared, plus foxglove leaves but no flowers, same with buddleia.
This year it's much more colourful.
I wonder if the last owners, or the council planted a butterfly friendly wildflower seed mix?
They all seem to be self seeding.