From the Ground Up

For the everyday person, grass is just grass. There’s no difference between the grass in our yard and the grass that lines I-40 or the grass that grows on the fairways of Pinehurst golf resort. But there is, in fact, a different grass for every purpose, climate and aesthetic. And until 2009, no one was in charge of breeding the best grasses for North Carolina’s varied climate. That’s where Susana Milla-Lewis came in, filling a gap in NC State’s existing strengths in turfgrass science, management and pathology as the university’s first turfgrass breeder.

“We’re right smack in the middle of the country,” she says. “You grow warm season grasses in the south and cool season grasses in the north, but we’re in what’s called the transition zone where you can grow both.”

Because our winters are too cold for warm season grasses and our summers are too hot for cool season grasses, Milla-Lewis determined early on that she could specialize in a niche of turfgrass breeding that improved the cold tolerance of warm season grasses and the heat and drought tolerance of cool season grasses. 

Driving around Wake County in 2009, Milla-Lewis saw landscapes and roadsides filled with cool season grasses. But breeding a new turfgrass can take more than a decade from start to finish, so Milla-Lewis focused on future needs: grasses for hotter summers and more severe droughts. Turf that uses less water, fertilizer, and pesticides and could tolerate shade better than existing varieties. It required the scientific version of a crystal ball. She chose to focus her efforts on warm-season grasses.

Her crystal ball was right: 2024 was North Carolina’s second-hottest year on record since 1895, according to the North Carolina State Climate Office.

The Turfgrass Breeding Playoffs

Starting a breeding program from scratch is like having an open casting call for grass varieties: anyone can show up, stars and duds alike. And it was Milla-Lewis’ job to assess everyone who came in the door, what star qualities they possessed (if any), where they came from and what they might be capable of.

It all starts with pre-breeding where she screens each plant for traits of interest. She then makes cross-breeds with the desirable traits, germinates the seed, grows the plants in a greenhouse and transplants them outside in a test plot. Her program has leveraged emerging technologies like genomics, marker-assisted breeding, high-throughput phenotyping and machine learning using drone data to support variety development.

Each test plant is sent to three locations. One is sent to the Lake Wheeler Road Field Laboratory where the disease pressure is high and the soil is poor. Another is sent to the Sandhills Research Station where the sandy soils allow her to test for drought tolerance. The third is sent to the Upper Mountain Research Station, which allows for high elevation testing of cold tolerance.

For three years, more than 1,000 grasses competed in the first round of the Turfgrass Breeding Playoffs. Milla-Lewis and her team assessed how each grass fared in all seasons, through every weather event and pest or disease outbreak. From there, the best 40 to 60 grasses moved onto the quarterfinals, undergoing more rigorous scrutiny for each desirable trait for three to four more years. 

The best five to 10 grasses moved on to the semifinals where larger sections of each grass were grown on farms across the state for another three years. These on-farm trials often revealed many more traits of interest, like sod quality from a grower’s perspective.

The finals of the Turfgrass Breeding Playoffs culminated with two to three contenders going head-to-head for Best Grass. They were planted in larger plots for one or two final years before one took home the winner’s trophy.

Championship Grass

If we had to wait 12 years to find out who won the PGA Tour or the World Series, we’d lose interest. But Milla-Lewis has been sticking with it for over a decade. Her hard work is paying off.

“She started with nothing and she’s already hit some home runs,” says Loren Fisher, director of NC State research stations and field labs. 

In 2021, she released the LOBO™ Zoysiagrass, a medium-textured, low-input grass that is very fast to establish and, perhaps most notably, has excellent color retention under drought and cold stress. In the Turfgrass Playoffs, it had the best performance under a range of uses, from low-management to higher-end spaces like lawns and golf course fairways. LOBO is not just grown in North Carolina, but has spread to states across the country and even overseas to sod farms in Brazil.

“A lot of times, these grasses are marketed at the national level, so it goes way beyond your wildest expectations to see how far these grasses can go,” Milla-Lewis says.

She then released SOLA™ St. Augustinegrass a year later. SOLA is an improvement over a North Carolina St. Augustinegrass called Raleigh that was released in the 1980s. Compared to Raleigh, SOLA has better drought tolerance, better turf quality, better disease resistance and, most importantly, much better shade tolerance. She has also released three tall fescue varieties in partnership with a breeder in Oregon.

Even though it took 12 years to release her first variety, Milla-Lewis says it will not take 12 more for the next one to come out. With a pipeline of contenders already assessed and established, Milla-Lewis can continue selecting for other traits of interest for different types of spaces or different climates across North Carolina and around the world. She anticipates releasing new varieties every few years with the support of North Carolina sod producers, private companies and other research institutions across the country. 

A Team Sport

Partnerships to develop the next best grass come in as many variations as the grasses themselves. Sometimes Milla-Lewis partners with breeders at other institutions to split up the workload: one tests for diseases and pests while the other produces seed and tests for yield. Or, she might work with breeders in different climates so they can each assess the same varieties under very different conditions, to get a better picture of their wider adaptation, all while sharing the findings and the royalties. In other cases, she works on sponsored research agreements with individual companies that support her breeding efforts in exchange for targeted variety development and testing.

But Milla-Lewis couldn’t do any of this without the farmers themselves. When the turfgrass contenders make it to the semifinals, she needs larger, active farms to grow the grass the way a farmer would, from seed and sod to harvest and regrowth. For her, there is no greater partnership than the one with the farmers who live and breathe turfgrass just like her. Their input has been invaluable. Whenever she has asked a farmer if she can plant turfgrass trials on their land, she says they respond with incredible generosity, always saying yes and asking what she needs to be successful. 

“It starts as a business relationship, then you earn trust, and then you develop these strong personal relationships with these people. They become friends, we’re all part of the sod family! It’s really quite wonderful,” Milla-Lewis says.

She is currently breeding for a coarser textured zoysiagrass and a St. Augustinegrass with even better drought tolerance. She is also working on new centipede grasses with better quality and seed production. If you look close enough, soon you’ll see Milla-Lewis’ handiwork in yards, fields, and roadsides all across our great state, with many more on the way.

This post was originally published in College of Agriculture and Life Sciences News.