I was waiting for someone else to answer this post,LOL.
It sounds like it is growing as a typical china. If you want something that grows or looks different, you'll probably have to remove it and plant something more suitable to your tastes. You could try some companion plants, but I don't think feeding and pruning is going to change it's DNA.

I would take a hedge clipper to it, and make it the size you want. I would not make it more than 1/3 smaller at a time. This rose wants to get big, and is also very healthy. The other thing to do is remove some of the inner branches- especially if there are some big ones that are stubby with little branches growing off them . Len511 has a good point- if it seems overgrown for the spot, then moving it is a good idea. Nothing worse than to wage continual battle with a plant too big for its location. If it does not have full sun, that may account for the scraggly growth. Some fertilizer can also help, especially something like a top dressing of compost.

Yes, Mutabilis is a China and Chinas are airy, twiggy, every-which-way growers. It will never be dense or compact. You don't have to prune it at all--just cut out the dead wood. Left to its own, it will grow to at 6' and maybe 8' with at least some blooms all the time and of course big spring and some fall flushes. It's not a mannerly, proper rose, but it is a very happy and hardy rose.

Thanks for all the replies! I chose poorly when I used the word "compact" -- I realize this is meant to be large and wild-looking, and it's got enough room for that. But from pictures I've seen of other mutabilis roses, I think the foliage on mine *could* be a lot denser. It's good to know I can prune it down to a smaller size. I hope that will help to fill in some leafiness eventually. I'll add some compost too.

Thanks again!

I had one get to nearly 10ft tall here, and that with hard freezes in winter.

I would whack back whatever stuck out too much, and in winter I would thin out some of the canes by cutting a few back all the way to the ground. It does not require precise pruning.

Mine was in a southeast-facing corner, so it did not get afternoon sun, but was still reasonably dense and floriferous. It always had bare knees at the bottom though, that's just how they are. I planted perennials in front of it to cover the bare cane bottoms. It got fertilized with a general rose fertilizer once or twice a year, in spring.

I agree with the selective thinning. I am not a fan of hedge trimmer pruning for chinas, as some very weird growth can result. Selective thinning means you carefully remove aged canes, leaving newer, vigorous wood to garner more of the plant's resources. The result is fuller rose, with fewer canes better nourished.

Mutabilis is a twiggy grower, and there isn't much about that growth habit you will be able to change. I happen to think that very selective, careful pruning may help you keep it within a certain size, but it is never going to be a dense 4 foot rose. 6 x 6 is normal for this rose in Texas and in much of California. It can get even bigger in really mild climates.

That said, I've seen it hedged to 4 feet in the median strip in downtown Milan. I wouldn't say it was beautiful, but it was novel.

I've seen it clippered into the form of a gigantic bonsai tree, too, but I doubt the rose appreciated the art.

I was looking at a 10-or-so-year-old Mutabilis yesterday. It has climbed way up into some adjacent oak trees. Planted wholly inappropriately next to a path, and the controls for an irrigation system, it must be hacked back enough annually to permit access to the path and the water valves.
It doesn't seem to mind that.
But no amount of shaping is going to make it into a dense shrub.

Jeri

It doesn't seem like Mutabilis has the "look" that you want. If you don't appreciate the "natural beauty" of Mutabilis, replace it with something more to your tastes. There are thousands and thousands of plants to chose from. There is no reason to try and "make" Mutabilis do something it is not genetically programmed to do. I hope I didn't come across as "preaching."

Robert