I've had one plant, actually it was a HOS so probably about 6-8 seedling in it when it was planted about 5 years ago.
It blooms a light pink and is beautiful.

It's the same clump now as it was second year in the ground, first year it bloomed.

No invasiveness with it for me, no seedlings popping up anywhere and I've never gotten any reseeds from it either and I don't collect the seeds.

Fran

Knautia macedonica self sows for me, I try to keep it deadheaded....interesting, brushing bees away as I try to cut off the spent flowers since blooms keep coming for such a long time :) I wouldn't say invasive but if left to form seed, I'll have some seedlings I'll need to pull in Spring. The plant itself stays in a gradually widening clump.

I live in zone 5 and do not deadhead and have not had a problem with it self sowing. It gradually grows larger, but all plants do that, not a problem for me at all.
Pretty flower, you will be happy

Ill let you know if I can ever get some to grow.

;>

Very vigorous re-seeder; I am constantly pulling them out of the lawn and losing the battle. I would imagine that some would consider them invasive. I think they're worth the work.

It sounds like it's worth a try, then. If anyone has Knautia Macedonia seeds they would like to trade, feel free to take a look at my trade list and see if there is anything that interests you. Thanks, everyone, for sharing your experience with this flower.

I got seeds from Diane's Flower Seeds last year and WS them. Got okay germination and planted out nice-size HOS back in July. I won't see bloom on them until next year so can't comment on them being invasive but Diane's website doesn't mention it.

Very vigorous re-seeder for me too. Worse than Feverfew, because leaves are much wider and seedlings grow thickly.
I regret planting it to these days.

I have plenty of Knautia seeds - all colors such as pink and burgundy mixed. If you want some for sasbe email me. I also have fresh mexican hat and shasta daisy. I could drum up some heliopsis and lychnis as well.

Very invasive where I have them (exposed site, full sun, well drained soil). They pop between the other plants and own their space. In a short period of time the new plants produce tall flower stems that give too much height at the front of the border where it was supposed to remain low, so for that reason I keep pulling them out every year (quite annoying) .

The initial 5 plants became easily more then 50 in a couple of years . They are easy to be pulled off the ground though. I would consider Knautia 'Melton Pastels a "good invasive" plant due the germination percentage and quantities of seeds produced from one plant being high, however they are beautiful, super easy to look after, trouble free and will attract tons of bumblebees and wildlife pollinators.