I had a similar problem. I removed the fence around my pool when I had the deck redone. I wanted a privacy screen close in so I used a combination of things. I made 5 trellises from 4X8 vinyl lattice and put them on landscape timbers about 2 feet above the ground and kind of framed them. Basically this made an 8 ft wide trellis with the top about 6 ft high. On two of these, i put Lady Banskia roses..they are evergreen. One one I am growing Confederate Jasmie and one one Carolina Jasmine (which isn't as thick a screeen as the confederate). The 5th trellis has another climbing rose but isn't really a good screen. I sort of placed these trellises at intervals around the deck toward the corners but not exactly symetrically.. In between these are a variey of other plants, viburnum which makes a bigger lush tree and lorepeltum for it's rich red coloration. The bed around my deck is of varying width from maybe five feet at the back of the pool to 10 feet on one end. So I also have room for compacta and some other hollies as well as day lillies, a few sago palms etc.. I used this other stuff for a low to the ground screen but also to give some texture /color differences. I've been shaping these other plants, some round, some square etc.. I'm definitely not a gardening artist, I just like to play and add stuff, but the effect is nice.

Have you tried power washing them?

How much sun does this spot get? My callistemon rigidus does really well in a 7 gallon container with low water. It seems to bloom almost all year round too. You can let them grow as a shrub, or what I'm doing, train them into a small tree. It's happiest with a lot of sun. I don't know how long I can keep it in a container though, it may grow out of it and I'll put it in the ground eventually. I didn't notice it's drip tube fell out of the container one day when I was moving it a little and a few weeks later it was still doing fine. Granted this wasn't in the middle of summer in full sun, I'm pretty sure that anything would die in that situation. If you don't mind a deciduous plant in a container, you could try a crepe myrtle. They grow as a small tree with multiple branches. I had a crepe myrtle in a container for a few years (I planted it in the ground this year) and it did fine with low water as well. It has a lot of showy flowers in the summer. This one isn't as drought tolerant, but if the spot is shady in the summer, you could try to find a Michelia Figo. I'm very happy with both of mine. The flowers have a pleasant smell in the spring and summer (smells kind of like a baking cake. Some say it smells like bubblegum, I can smell that as well). They are perfect for containers as they grow slowly and never lose their leaves. They look a lot better when the soil is kept constantly moist in the summer. They pretty much require shade in the summer here in their first few years. These are just what I've experienced so far, and I'm sure there are better plants for containers than these, so hopefully someone else will have some suggestions too.

The part beyond the branch may lose vigor. But if or when the tree grows over the girdle things will return to normal. If it's just a branch it's not serious even if you have to remove that part. I've done it to the top half of a tree. It still hasn't grown over the girdle but I think it will.