Definitions of immortal include “living or lasting forever” or “lasting a long time; enduring.” A reader recently commented on my article about holiday plants saying she had a Christmas cactus that is over 40 years old. A tree in Sweden is said to be growing on a rootstock that is 9,550 years old. A downed bristlecone pine in California was proven to be 4,768 years old when its rings were counted.The plant kingdom has the seeming ability to stay forever young through vegetative propagation. In the Swedish example above, the same genetic rootstock has lived for thousands of years, producing …