They grow like weeds here, I'm always pulling them out and I'm on heavy clay. I wonder why they haven't worked in your garden.........not that it matters now. I hope they work in your new one 👍 @ublaszko
Perhaps my garden is not sunny enough as it only gets sun between mid-March and mid-October. Or the soil holds too much moisture. I have the same problem with salvias. I ended up potting up my salvia and mixing compost 50/50 with perlite but I read sea holly doesn't like to be moved so I have to start with a new plant.
Yes they are quite big, I did wonder whether it was a hornet so I've been looking it up and it looks like it might be an Asian Hornet, there is a big invasion of them this year, they can eat up to 80 honey bees a day @bluefox23