Despite steady rain during the San Francisco 49ers Divisional Playoff game Saturday night, the playing surface at Levi's Stadium was greener and healthier than it’s ever been at this time of year, thanks in part to a bank of grow lights that arrived in mid-November.
As reported by The Athletic, head groundskeeper Matt Greiner prepared for the game by covering a third of the field at a time with neon pink lights. He said the movable rigs contain red- and blue-light waves that encourage photosynthesis, as well as infrared lights that help warm the surface temperature — all of which encourages growth.
Nick McKenna, the assistant athletics director at Texas A&M and the former president of the Sports Field Management Association, said the technology has its roots in the Netherlands, where it was used to help tulips grow in low light, The Athletic's Matt Barrows reported. In the U.S., Major League Soccer has used grow lights on its pitches, as are other NFL teams, including fellow playoff survivors Kansas City and Baltimore. The Chiefs' field at Arrowhead Stadium held up well despite their Wildcard game played Jan. 13 in subzero temperatures, and the Miami Dolphins have used the grow lights because the awnings inside Hard Rock Stadium, designed to shield fans from the hot South Florida sun, also rob the field of sunlight.
“We’ve got these newer stadiums where a lot of it is about the fan experience,” McKenna said. “You want the fans covered and protected from weather. So they’re building them more vertical where you’re creating these unprecedented shade lines. And at the end of the day, grass is a plant. It’s got to have a certain amount of light.”
Even a wide-open stadium like Levi’s doesn’t get enough light in the winter, according to Barrows report. The suite tower on the west side of the venue blocks a lot of the light, and the warm-weather Bermuda grass that makes up the bulk of the Levi’s playing surface typically goes dormant in late November.
"The grow lights are designed to keep it awake a little longer," Barrows wrote. "Greiner said the north side of the field gets more natural light than the south side, which is why the grow lights have spent more time on the south end of the field. He said sensors in the field that measure everything from light to soil temperature to moisture content suggest the grow lights are working. So do less scientific methods such as how often his crew has to cut the grass or how much paint is needed in the end zones, logos and other areas."
“We’ve never had a better stand of grass in the south end zone,” Greiner said. “We’ve never grown out of paint as much as we have in the south end zone. It’s been drastically different.”
Greiner said the grow lights will never be able to replicate the summertime sun. But he said all of the measurements he makes — including the rotational resistance of the grass, which essentially determines how it will hold up to the pounding of a three-hour football game — have remained higher this winter than they have in the past, Barrows reported.
The field, which endured an early history of instability, has been under less stress lately. In 2019, the 49ers had home-field advantage throughout the playoffs on the heels of a December in which Levi's Stadium hosted two 49ers games, the Pac-12 championship and Redbox Bowl. The stadium didn’t host any college games in December 2023.
According to Barrows, the 49ers have used the same surface since Ed Sheeran played a concert at the stadium on Saturday, Sept. 16. New grass was rolled in the following Monday and Tuesday, and the 49ers hosted the New York Giants on Thursday. Greiner said he swapped out what he calls the “gut” — the well-trafficked section between the numbers — after the a Jan. 7 game against the Los Angeles Rams.
“If you’re starting off with a superiorly strong stand of grass, and then you add in the elements such as the grow lights, that’s how you can sustain these fields,” he said.
The 49ers will host the Detroit Lions at Levi's Stadium in Sunday's NFC Championship game.
