The Drilling Radishes of St. Louis

MVVA deploys a (sort of) edible ally in its renovation of Dan Kiley’s Gateway Arch landscape.

By Zach Mortice

Tillage radish is similar in shape, size, taste, and color to daikon radish. *Image courtesy of MVVA.*

Oilseed radish, or Raphanus sativus, goes by the name “tillage radish,” “radish ripper,” “fracking radish,” and the comic book-worthy “turbo radish.” It can reach its two-inch-wide taproots down six feet, breaking up compacted soil and rebalancing nutrient levels, and is commonly put to work as a cover crop in agricultural fields. But the designers at Michael Van Valkenburgh Associates (MVVA) found another, more high-profile use for them: to remediate the soil during the renovation of the Gateway Arch grounds in St. Louis, one of the largest and most important landscape revamp projects in the nation. This reimagining of Dan Kiley’s mid-20th-century landscape is using an unprecedented application of soil-remediating vegetation into this sort of sensitive and historic National Park Service property, says Adrienne Heflich, an MVVA senior project manager.

It’s one sort of drilling operating that, even though it’s in a national park, is entirely welcome.

MVVA’s plan makes the park more flexibly programmed, better connected to the surrounding city, and sets out a plan for more sustainable landscape maintenance practices. Nearing final completion after seven years, the project will celebrate the opening of its North Gateway section on April 8.

Radishes grow in the shadow of Eero Saarinen’s Gateway Arch in St. Louis. Image courtesy of MVVA.

The radishes were planted in the early fall of 2015, surrounding the arch grounds’ two ponds, and near the train tracks that slice through the site. This species of vegetable grows rapidly through the fall, forcing its way into soil with thick roots (hence the “fracking” and “turbo” tags) before dying off in winter. The radishes rehabilitate soil by using their roots to break up and puncture the ground, creating pores that allow water and air to better infiltrate and circulate. The presence of these roots also helps to rebalance soil nutrients.

It’s a more delicate way to remediate soil without digging up the earth with excavators and replacing it with new soil entirely. And unlike in most urban parks, “there’s a lot of things about the arch grounds that make it uniquely well-suited for cover crops,” Heflich says. First there’s its huge size. Kiley’s original landscape is 91 acres, and MVVA planted 400,000 radishes across 12 acres of the site. That means MVVA could use mechanical agricultural seeding equipment to plant the radishes. And cover crop remediation doesn’t risk damaging what lies below such a sensitive and historic site. A National Park Service property, the Jefferson National Expansion Memorial, on which the arch sits, contains archaeological relics dating back to St. Louis’s earliest days, and keeping dump trucks and clawed excavating shovel buckets off the site protects these artifacts. (Beneath the soil that Eero Saarinen’s quicksilver arch sits on are what Heflich calls a “cosmopolitan mix of old city structures,” including remnants of the city’s former merchant waterfront, and fill from construction at Lambert Field, St. Louis’s airport.) Finally, using radishes to refresh this soil means that the hilly topography on site could be left intact, instead of scraping it apart and then building it back from scratch.

MVVA Senior Associate James Smith with a tillage radish, which can grow two-inch-wide roots down six feet. *Image courtesy of MVVA.*

“This project was an attempt for the National Park Service to reconsider decades of more conventional fertilizer and herbicide ways of landscape management, and look at more sustainable ways of managing landscape space that take into consideration nutrient cycles and biological activity in soil,” Heflich says.

Tillage radishes were planted around two ponds to the north and south of the arch. Image courtesy of CityArchRiver Foundation.

As thick as a fist and as long as a forearm, the ivory-colored oilseed radish is closely related to the daikon radishes that you might see at Asian grocery stores. It tastes like daikon as well. “I tried to eat them,” Heflich says. “The squirrels were eating them, and the birds. I wouldn’t recommend it, though. There’s no farm-to-table angle on this.” Urban soils from exceptionally affected sites don’t make a good place to grow vegetables that are reliably safe to eat, and if you deploy radishes to fix soil, they lose a little something in the bargain. It’s urban farming, of a sort, without edible produce, but still probably a deal worth making.

Zach Mortice is a Chicago-based architecture and landscape architecture journalist.You can follow him on Twitter and Instagram.