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Horticulturist raises an agave whose flowers rise more than 20 feet into the air

By Adrian Higgins
Washington Post Gardening Columnist
Thursday, August 19, 2010; DZ10

How many movies have they made where the hero saves the day and then . . . croaks? If you want real pathos, look in your garden.

The plant world is full of tragic heroes who give everything only to die. Consider the pretty larkspur of late spring, which pokes a feathery little leaf out of the ground in winter. In May it sends up a two-foot flower spike that decorates the garden, sets seed and then journeys to its end.

A lot of plants are killed by frost; they're simply tender. But true annuals including the larkspur are programmed to self-destruct after reproducing once. Such a plant is called monocarpic, which is Greek, roughly, for once fruiting.

We take this death struggle for granted. The larkspurs bloom in May in the prelude to an abrupt demise alongside poppies and sweetpeas. While we see spring as the season of renewal and hope, the poor carrot puts its all into producing a platform of white flowers. Little bees and wasps show up to fertilize the plant. Thank you, says the carrot, then it dies. It's a strange world.

For plant geeks, monocarpism becomes really cool when a plant takes years to flower. Many bamboo species are monocarpic. "Nonsense," you say, "I can't get rid of the stuff." Well, it's just that some bamboo species take more than a century to flower. And running bamboos, as opposed to clumpers, can die off in part but carry on as near separate organisms by the way they spread.

In Washington, the prize for monocarpic magnificence this summer goes to Bill McLaughlin, a horticulturist at the U.S. Botanic Garden, who likes to take native plants that aren't considered too hardy here and push the envelope. He does this at the Botanic Garden's Southern Exposure display at the main conservatory near the Capitol, but the action shifted recently to his own garden in South Arlington.

About 14 years ago, he placed a rough-leafed century plant (Agave scabra) in the corner of his front yard. Agaves are famous for their fleshy, tapered leaves, which are armed with spikes and radiate from the plant's center, but they are not well-known for their winter hardiness. They are found in the high deserts of Mexico and the American Southwest. In Washington, they are grown either as summer tropicals or in greenhouses, but not in front yards within earshot of Shirley Highway.

Put it down to the heat-island effect, superb soil drainage, global warming or all three, but McLaughlin's agave made it through the first few winters and became a fixture alongside his driveway. With each passing year, McLaughlin looked to see whether the annual spring growth would be more than just a fresh set of leaves. It had gone, after all, from a baby succulent just eight inches across to a mature agave five feet in spread and height.

The unmistakable flower buds began to show in late June and started to shoot up like a firework, appropriately, around Independence Day. The stalk grew three to five inches a day and eventually became four inches across at its base. In time, flower clusters were held aloft like a candelabra, but more than 20 feet in the air. The wispy flowers arose from purselike bases, the blooms a golden yellow that intensified as the sun rose and set. They were sticky with nectar, and sweet-toothed insects that had never seen an agave blossom must have thought a carnival had come to town.

When I went to see this phenomenon last month, a column of black ants was marching upward, following scent trails left by scouts. At the top, the flowers were alive with bees big and small. "I believe in nature it's a bat-pollinated species," said McLaughlin, craning his neck skyward. "I don't have this type of bat here, and I don't have another agave in the neighborhood, so it's not going to set any seed."

Although the flower stalk looked solid, the plant was showing the first signs of collapse. The leaves, for years unmoved by exterior forces, were beginning to sag and the central stem to wrinkle.

McLaughlin had come to terms with its demise, and noted the presence of a few baby agaves in the orbit of this withering giant. "I've been waiting for years for this," he said.

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