Laura ponders Bradford pear trees, which, soothingly line the streets of Cambridge, but which also tend to die off fairly easily and stink up the joint after they flower:

.. the trees tend to self-destruct. Not as in, "KABOOM" - as in, if they are not pruned as they grow, their tightly-crowded branches push away from the too-narrow, thinly-barked trunk, opening their thumbprint shape into more of a round baby toenail stunted with fungus, leaving them susceptible to wind damage in the warmer months and ice damage in the colder months. ...