Tropheus,
Were I in your same situation with a camphor tree invading a hedgerow of palmettos, what I'd do would be to spread some barrier cloth/paper/tarp/etc. over the palmettos as a protection for them and then give that camphor tree a good shot of RoundUp (or similar) –on a dry, windless day.
The RoundUp should do in the camphor tree down to its roots yet the palmettos will have been protected from the RoundUp by you having covered them well during the spraying of the intrusive sapling tree.
Once the camphor sapling has died you can prune its trunk down even with top of or just below the level of the palmetto leaves. The remainder of the dead stem will eventually disintegrate.
OK — HTH
Paul M.
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