As long as the camellias aren't diseased (fungal, usually for camellias) they're safe to compost.

If you're composting a whole lot of them (making them a large part of your compost), they can create compost with low pH, though.

Some "authorities" state emphatically that you should not compost any part of the Camelia, without giving any reason while others suggest that you can. Most every study I have seen says finished compots will have a neutral pH no matter the source material.
"Paulowia Tomentosa" is considered a noxious weed so I would be careful about composting any part of that tree unless I could be sure the seeds were not viable. I once, inadvertently, picked up some leaves containing material from a Tree Of Heaven, "Ailanthus altissima" and have found seedlings from that growing all over the place since.

The only reason some sources say not to compost camellias is because the thick, glossy evergreen foliage takes a long time to break down and decompose. Chopping them up (run over with your lawnmower) will accelerate the process. Evergreen magnolias and English laurel are often referred to similarly for the same reason. And English ivy.

Acidic ingredients do not make compost acidic. Compost tends to neutralize any pH imbalance regardless of ingredients and as was stated in the previous post, tends to be almost neutral in its finished state.

Neutral compost is ideal and easy to obtain with a wide range of sources, but it is dependent upon source materials in some cases.

The act of composting, itself, doesn't necessarily lend itself it neutral compost until it's totally humus. A healthy/balanced compost is pH neutral, but you can skew the pH of your compost (and in some cases lessen fungal or bacterial decomposition) depending on your source material if it's major component.

If you make a nearly total pine needle compost you'll have some acidic stuff (and it will take a long time to break down). It's popular with some blueberry growers around here. Pine needles added to a healthy mix of compost will generally not effect the pH. For the same reason, top applying pine needles as a garden mulch will generally not raise your overall soil pH unless you apply a whole lot over many many many years.

I was addressing a mostly/extreme addition when I was speaking of compost pile makeup above.

That said, eventually all of the compost will go to a nearly neutral pH humus....but even the best managed composts are rarely total humus when it's applied. Almost everyone's compost is still in the act of decomposing and releasing/complexing nutrients/acids/bacteria/fungi when it's garden applied. The age and state of decomposition plays a part here.

This post was edited by nc-crn on Sun, Mar 17, 13 at 18:54