After it's finished flowering, lift the edges and cut down into the plant. If you want to transplant parts of it to another area, make sure you dig up the attached roots without disturbing them too much. Water well.

I just put 2 dianthus in yesterday. I can only hope mine will get that big and beautiful. But to your question, what's the worst that can happen? If you divide some and the transplanted portion doesn't make it, you haven't really lost anything. I believe that plants will do what they are created to do. I say if is too big, in the early fall, divide some of it.

It won't divide, but usually a piece has rooted itself right where it is. Just dig out that piece.

i have never had a lot of luck with these.. long term ...

as such.. if one got that big for me.. i would surely be moving OTHER THINGS.. to give it more space ...

you are in a box.. look outside.. before your slaughter this beauty ...

ken

It's definitely dividable, but you have to pay attention to how its rooted. Often it makes a really wide mat with not that many roots going deep into the soil. So if you divide it you want to make sure you get some of those deep roots, not just that mat that sits on top. I love Firewitch and I divide it and move it and move around the seedlings all the time. It's a tough plant so it can handle indignities. Good luck with it!

Thank you for all your suggestions.

Ken, That is why I came here to ask for some advice. I witnessed one of my neighbors divided his beautiful dianthus (several of them as they grow too big) last June, they all died. But I thought that could be due to the very hot and dry summer we had last year.

Karin, That is a good tip and I may give it a try in the fall when I typically do the divisions and moving, etc. Right now it is so beautiful and I do not have the heart to touch it. Ken is right. The other plants around it is much easier to be moved to create more space (it is already a little over 2 feet wide), at least for a couple of more years.

Thank you again for your advice.
Vivian

FWIW, the plant pictured above is not 'Firewitch'.

If Firewitch is a cultivar that doesn't come true to seed, then it seems like dividing it would be the only way short of the lab to get more of it. I have started seeds from mine and they aren't quite like the original, but still nice. If I were going to move it or try to divide it I would do it either after its flush of bloom is done, so it would have time to recover before winter sets in here, or next spring. I haven't had a lot of luck with moving or planting perennials in the fall. Spring, about March or so before they start to grow, is my best time to move things around. Ideally I would wait until next spring.

Could it be 'Bewitched'?

I planted it 5-6 years and at that time I did not pay attention to the tag. Later on after googling, Fire witch is the closest match I can find. Even though some on line picture shows taller spikes.

Bewitched has different color shade.

If anybody can help ID, that would be great.

Thank you.
Vivian