A tree is growing in the middle of AT&T Park, doing so inrelative seclusion even amid sellout crowds of 40,000-plusfans. A giant sequoia among the Giants ? No. Another palm like those 24 in Willie Mays Plaza? Nope. Peeking out from behind the centerfield wall is a 9-foot tallavocado tree that sprouted from a groundskeeper's meal 10 yearsago.