In our region (the Gulf Coast) one of the best companions is hydrangea. They are not evergreen, but they combine well with camellias because they bloom almost the opposite time of year, each complementing the other. And just when autumn arrives the hydrangeas shed their leaves, retreating from the garden stage as the camellias begin to show off their winter wares.

There are many other companions that do well, but we have come to like this combination.

thank you for the suggestion! i love hydrangeas!

It's nice to use something that is deciduous, I think! At the very least, you should come up with something with a different form, leaf size, etc.

I have late spring blooming gardenias and deciduous azaleas (Dodd's confederate series) around mine.

What about impatiens? That's what I have growing at the base of my camellias. It's a pretty sight right now with all of them blooming simeltaneously.

Even we all are in US but California is different in climate. Ca has dry season from about May to October. The ground in summer time is bone dry unless your camellia area and the area for companion plants are all equally to water properly. If your water system is geared to water more to camellia and possibly less water at surounding larger area, the other plants will send sucker roots to tangle your camellia root.

In humid part of US and in southern China, most plants( from weeds to forest timbers) and camellia can grow side by side without any problem of root interference.

I have a few suggestions:
Pittisporum (Dwarf Variegated)
Gardinia jasminoides 'Frostproof' short and fragrant
Colocasia 'Purple Stem' red stemed small Elephant Ears
San Gabriel Nandina for fall color
And then add a few annuals for color

Here is a link that might be useful: GardenWeb