Crews use radishes to boost soil at Arch grounds

ST. LOUIS -- An effort is underway to provide fertile soil as the groundwork for landscaping at the Gateway Arch grounds in St. Louis.

In late September, contractors planted about 400,000 radishes in an effort to soften the compacted soil at the national park, which is largely low-quality clay fill, The St. Louis Post-Dispatch reported.

Although most of the radishes froze and died over the winter, they helped till the soil by sending their thick tap roots almost 2 feet deep and leaving hundreds of thousands of long, skinny holes in the ground, and they're depositing nutrients closer to soil surfaces.

"It actually feels almost like you're walking through a forest," said Arch grounds contractor and arborist James Sotillo, one of the brains behind the plan. "That's the beauty of these radishes. As they grow, they're releasing all of these incredible metabolites into the soils."

Officials at the National Park Service and CityArchRiver foundation have said the old ash trees on the Arch grounds weren't going to last much longer because the soil isn't fertile enough to support big trees with long lives.

To remedy the problem, contractors also have matched compost with the grasses they're planting so the right nutrients and organisms are in the ground. They're brewing a special concoction they've been spraying every spring and fall before construction started.

About $5 million has been spent to buy and truck in tons of specific soil blends -- enough to cover 18 football fields in three feet of dirt.

"When you think about ecology, you have to have good soil," said Susan Trautman, executive director of the regional trails organization Great Rivers Greenway. "Better soil means trees can live longer, develop deeper roots, so they can sustain over time."

It's unclear how much the soil effort has cost the project upfront, but architects believe it will save the Park Service money in the long run.

Work on the $380 million CityArchRiver renovation should be completed next summer.

Nearly 900 London plane trees will be planted to replace the ash trees.