Rob wrote in message
...

do I need to do something, eg. sand or wash it in order to make it the same
color as the rest of the table?

Rob, this is going to be a contrarian view, but I'm basing it on about forty
years of experience with teak, having owned and restored a classic wooden
sailboat through all those years.

First of all, that dark area will lighten eventually under sunlight no
matter what kind of finish you put on it, even a high-UV-protective finish
like marine spar varnish. And it won't take too long either. So go ahead and
finish it if you want, but once you do you'll be committed to maintaining
the finish.

But on the other hand, for wood that's left unfinished, teak is about the
finest wood on the planet. It's durable and rot-resistant, and when left
alone turns a nice silvery grey, with a lot of character. I have a deck area
on my boat that's never had finish on it during the entire sixty years of
its life. Every spring I scrub it down with soap and water, with a
soft-bristle brush so as not to erode the softer grain. Sometimes I squirt
in a little bleach water if the wood seems a little dark.

For lawn furniture, if you really want to brighten it up, spray it down with
some of what the hardware stores call '30-second cleaner' or something like
that, scrub it lightly, hose it down with clear water, and let it dry. It'll
knock your socks off.

Tom