SOME PLANT.

For fifty years, the Agave americana at the New York Botanical Garden's Enid A. Haupt Conservatory led an exemplary, if somewhat artificial, life. Five feet high and ten feet across, the specimen would occasionally drop one of its fleshy, gray-green leaves or send up a new shoot, known as a "pup." What, exactly, got into the agave this spring no one is quite sure, but in March the plant began to swell noticeably. The conservatory manager, Francisca Coelho, went home one Friday, and by the time she returned, on Monday, the swelling had given rise to a three-foot spike. The spike continued to grow, Jack-and-the-Beanstalk style, at a rate of nearly a foot a day, until it threatened to break through the glass above. At that point, Coelho had an opening made for it in the roof, and it kept on growing until it had reached a height of thirty feet. The tip of the spike is now covered with dark-green buds.

A native of Trinidad, Coelho is slim, with dark, shoulder-length hair and a slightly distracted manner. Standing in the conservatory's American-desert wing the other day, she noticed two tiny weeds sprouting from a crack in the pathway. A very important donor was scheduled to stop by any minute, and Coelho told a gardener who was sweeping up to make sure that the sign in front of the agave was polished before he arrived.

Agaves, Coelho explained, are monocarpic, which means that "once they bloom, they die." How long this takes varies from species to species; in the wild, the Agave americana, a native of northeastern Mexico, flowers after anywhere from ten to thirty years, and expires in a shower of bright-yellow blossoms. Though the buds were still closed, the conservatory's specimen ...