Never would I put varnish or any other film-forming finish on anything
going outdoors. When the sun destroys the finish (and it will) the
result is a flaking mess. I'd use a penetrating oil finish that you
can just renew instead of having to sand off the old finish to put the
new one on. Most cedars will form splinters if you just let it
weather.

DonkeyHody
"There's a difference between doing things right and doing the right
things."


I'll second this!! I put a marine spar varnish on a cedar sandbox and
after a year, that's what I have, a flaky mess!!