I have heard that there is no limit on the growth of trees, but then why do some trees, such as boxelders and poplars, tend to live shorter than redwoods, for example? Some advertisements for improved lombardy poplars state that their trees have an extended life span, up to 75 years?
Although most plants can potentially reproduce sexually, there are some plants that effectively always reproduce by shedding off branches that when fall in the right conditions, grow into new 'clones' of the same tree, which the exact genetic material. In these cases, it is advantageous for the tree to be able to survive as long as possible. Plants that reproduce sexually by the cross of two different individuals have a recombined genetic material in every generation, and the survival of that plant with that new genome is usually shorter.