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50 million footprints play havoc with the grass on the Washington Mall

The grass that covers the Washington Mall, the most visited national park in the United States, is in bad shape. The footprints of 25 million visitors are part of the reason why.

By Adrian HigginsThe Washington Post/WP-LAT Syndicate / November 5, 2009

Twenty houses, plus tents and trailers, were placed on the Washington Mall in October for the Solar Decathlon. Such events, plus millions of visitors each year, contribute to the trampling of the grass on the Mall, America's most visited national park.

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Fall brings the Washington Mall to its annual low point. This is when many of the turf panels have been beaten back by so many feet over the previous six months that calling it turf is an act of generosity. Some of the rectangles of lawn are no more than a blend of bare soil and weeds. "Soil" might also be a misnomer.

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"The maximum (soil) density we have measured was about equivalent to cinder block," said Robert DeFeo, a horticulturist with the Mall's stewards, the National Park Service.

Each fall, the pattern of rejuvenation repeats itself in an exercise that calls to mind Samuel Johnson's view of a second marriage: the triumph of hope over experience.

The landscape crews might add a top dressing of compost, rough up the ground with an aerating machine, and then sow the seed in slits.

By April, when the new grass looks green and perky, the fences come down, and then it is flattened by ballplayers, tourists, protesters, joggers, and all the rest.

This is America's most beloved civic space, and it is meant to be used to commemorate, celebrate, and recreate, but as increasing numbers do a number on the greensward, the suffering is evident, and the solution to it less so.

"If you had 25 million people walking through your front yard — that's 50 million footprints, assuming everybody has two legs — it's reasonable to expect it would look the same way," said Bill Line, a Park Service spokesman.

It's not just feet, though. It's tents and other structures for special events. (Twenty houses, plus tents and trailers, were placed on the Mall in October for the Solar Decathlon.) One year, during a military display, there were tanks.

The Mall is the most visited and trampled park in the nation, particularly its core between Third and 14th streets. This 70-acre axis is nearly a mile long and defined by eight grass panels bounded on each side by corresponding lawns shaded with hundreds of American elm trees.

The Park Service fences off the vulnerable elms for several months a year, but the central panels take the heaviest beating. The idea is that the turf can be repaired a lot easier than stressed old shade trees.

Apart from the damage to the blades of grass, sufficient injury to a clump will kill off its regenerating crown. The biggest problem is with soil compaction, which presses the top few inches into a block that robs the roots of the air and moisture they need.

Compacted soil drains poorly and causes waterlogging that can rot the plants. Of course, putting a tent or flooring over the grass for a few weeks will take away its food source, sunlight.