Many people think of California as San Francisco and Los Angeles from end to end, but there are some truly amazing natural areas in the state. Some of them are home to the tallest, largest and oldest living things on earth.

http://en.wikipedia.org/wiki/Pinus_longaevaOldest "non-clonal" plant in the world. There's one who's location is being kept secret that is over 5,000 years old.
http://en.wikipedia.org/wiki/Sequoiadendron_giganteum Biggest single trunk tree in the world. I worked in this area for several years and standing next to a tree over 2,500 years old that's trunk is as big as a small house is very humbling.
http://en.fishki.net/comment.php?id=104692 Tallest trees in the world. Redwoods National Park is on the far NW corner of the state and I've only been there once and definitely want to go back and spend more time. Cool, misty and quiet. They filmed "Return of the Jedi" in this area (Endor scenes).

I love the redwoods. I used to go camping there as a child, and is still my favorite place in the world to go. Sadly now-a-days not so much. My wife refuses to go camping.

That's disappointing. Camping is a good way to bond as a family.

I've never been to Cali so I can't comment on the trees there. I live really close to Algonquin Park so that suits my tree needs.