There are several choices:
Giant Sequoia National Monument, east of Porterville, California (and the northern section is east of Fresno). americansouthwest.net/california/giant-sequo…
Sequoia National Park, east of Visalia, California. http://www.nps.gov/seki/index.htm
Kings Canyon National Park, east of Fresno, California. also http://www.nps.gov/seki/index.htm
The Grant Grove in Kings Canyon NP is about a 1-hour drive on Highway 180 east of Fresno. It contains the General Grant tree, the third-largest tree in the world (by volume). It is beautifully situated in its grove with paved trails winding through the grove. That is a very popular and sometimes crowded grove, but possibly the easiest to get to for you.