The Oldest Trees on the Planet Trees are some of the longest-lived organisms on the planet. At least 50 trees have been around for more than a millenium, but there may be countless other ancient trees that haven’t been discovered yet.
Trees can live such a long time for several reasons. One secret to their longevity is their compartmentalized vascular system, which allows parts of the tree to die while other portions thrive. Many create defensive compounds to fight off deadly bacteria or parasites.
And some of the oldest trees on earth, the great bristlecone pines, don’t seem to age like we do. At 3,000-plus years, these trees continue to grow just as vigorously as their 100-year-old counterparts. Unlike animals, these pines don’t rack up genetic mutations in their cells as the years go by.
Some trees defy time by sending out clones, or genetically identical shoots, so that one trunk’s demise doesn’t spell the end for the organism. The giant colonies can have thousands of individual trunks, but share the same network of roots.
Pando
While Pando isn’t technically the oldest individual tree, this clonal colony of Quaking Aspen in Utah is truly ancient. The 105-acre colony is made of genetically identical trees, called stems, connected by a single root system. The “trembling giant” got its start at least 80,000 years ago, when all of our human ancestors were still living in Africa. But some estimate the woodland could be as old as 1 million years, which would mean Pando predates the earliest Homo sapiens by 800,000 years. At 6,615 tons, Pando is also the heaviest living organism on earth... http://www.wired.com/wiredscience/2010/03/old-tree-gallery/all/1?npu=1&mbid=yhp 
