Weighty issue bears down on Washington's cherry blossom

A gaudy cavalcade of dancers, floats and musicians will make its way along Constitution Avenue in downtown Washington today for the city's annual Cherry Blossom Parade. But, unknown to most participants, the gorgeous blooms around the Tidal Basin that are the pretext for the whole thing are under a subtle but potentially mortal threat.

A gaudy cavalcade of dancers, floats and musicians will make its way along Constitution Avenue in downtown Washington today for the city's annual Cherry Blossom Parade. But, unknown to most participants, the gorgeous blooms around the Tidal Basin that are the pretext for the whole thing are under a subtle but potentially mortal threat.

The problem, in technical terms, is soil compaction, in layman's language, the relentless pressure of the feet of visitors - an expected one million for this year's blossom season alone - as they crowd narrow paths to experience one of the signature sights of the US capital.

Early each year, a horticultural ritual unfolds, as the progress of the buds is monitored and the precise date of the blossom's appearance is calculated and re-calculated, adjusted in accordance with temperature, precipitation and predicted future weather patterns.

This year, the stars are perfectly aligned. The parade, the climax of a fortnight-long festival, comes on the very day the 3,700 trees will be at their finest, an explosion of pink and white blossom framing the white marble Jefferson Memorial and other landmarks of Washington.

But, largely unnoticed, the roots of many of the trees are slowly being starved to death by the sheer weight of visitors, whose numbers have only grown with the proliferation of monuments around the Mall.

As the soil is pressed down, the roots lose access to air, water and nutrients. If they move nearer the surface to breathe, they face drought and heat stress in Washington's torrid summers - capable of baking solid the clay soil native to the region.

The city's obsession with its cherry blossom can be dated to 1912, when the mayor of Tokyo gave 3,000 trees to Washington as symbol of the enduring friendship between the US and Japan (a friendship briefly but rudely interrupted by the attack on Pearl Harbor in 1941).

Japan knows something about cherry blossom, which is the country's unofficial national flower: tourists flock there each year at the end of April for the "Golden Week" of three public holidays to admire the cherry trees in bloom.

Of the original plantings in Washington, only 125 or so remain, mostly in the areas that are either off the (literally) beaten track, or protected by fencing.

Today there may be more trees than in 1912, but their longer term prospects, if nothing is done, are increasingly precarious.

The obvious answer would be to fence all the trees off and encourage everyone to enjoy the gorgeous spectacle from a distance. But according to Diana Mayhew, executive director of the festival, that possibility "hasn't even been a consideration".