By Eric Watkins, University of Minnesota
Perennial ryegrass finds its way into most turfgrass seed mixtures for home lawns, parks, and other types of mowed landscapes in Minnesota and most of the northern United States. Quick germination, rapid establishment, dark green color, and, most importantly, lower cost than other options, give this species an almost permanent place in the seed bag. This popularity belies the many weaknesses of this grass, including problems with winter, summer, heat, drought, disease, and shade.
Over the years, our team at the University of Minnesota has spent significant effort trying to figure out how to make perennial ryegrass more winter hardy. To date, we’ve had some success, especially with cultivars released primarily for their ability to survive winters in the turfgrass seed production fields of far northern Minnesota. Still, there are winters when these new varieties fail even in seed production fields, just like the varieties we haven’t spent time developing.
Turfgrass managers in Minnesota are well aware that this past winter was not kind to lawns and other turf surfaces. This lack of charity extended to our turfgrass research plots, where we try to identify the best grasses so we can cross them with other best grasses, and hopefully make some progress on our elusive winter hardy perennial ryegrass goal. As a turfgrass breeder, an ideal winter will kill some perennial ryegrasses, but in a consistent manner. Hopefully those perennial ryegrasses that aren’t fit for our winters will die, and those that have the potential to thrive here will live. Let’s take a quick tour of the University of Minnesota perennial ryegrass research plots and see how things are looking after the 2025-2026 winter.
Stop 1: Perennial ryegrass under ice
What are you looking at?
You can see in this photo what looks like 9 larger plots; each of these is a different ice treatment, repeated 3 times. We had 3 blocks that served as a control (no ice), 3 blocks that had about 90 days of thick ice that started in late December, and 3 blocks that received ice later in the winter/early spring that remained for about 2 weeks. Each block contained 16 different perennial ryegrass selections or varieties. The squares in the picture that look white are the 90 days of ice plots. There were no differences between the short-term ice and no ice; this is mostly due to weather conditions not allowing for longer-term ice encasement. We had hoped to see how late season ice, formed while plants are emerging from dormancy, compares to ice that forms on fully dormant turf.
What did we find out?
Ice cover for 90 days completely killed all 16 perennial ryegrass entries. Two weeks of later winter ice caused minimal damage. No ice = No problem (not always the case: see below!).
What should you do about it?
Don’t plant perennial ryegrass in low areas where ice might form over the winter (turfgrass professionals already knew this).
Stop 2: Perennial ryegrass maintained as a golf green
What are you looking at?
This trial is part of the SCANGREEN project, led by turfgrass scientists in Norway who are also members of the WinterTurf team. The goal of this project is to first identify species, and then cultivars within species, that can survive harsh winter conditions on golf greens with minimal inputs. This is critical in Norway and other Nordic countries due to restrictions on various chemicals. In the center of this image, there are two long strips running vertically: the strip on the left has Kentucky bluegrass cultivars - they all survived. The strip on the right that looks like dead grass is perennial ryegrass; they pretty much all died.
What did we find out?
Of the species tested in this trial, perennial ryegrass was the worst at surviving low-input winter conditions.
What should you do about it?
Don’t plant perennial ryegrass on a golf green in Minnesota (you didn’t need to know this).
Stop 3: Perennial ryegrass National Turfgrass Evaluation Program trial
What are you looking at?
This is the 2022 NTEP perennial ryegrass trial. These plots have now been through four winters, and until now have held up pretty well. In these photos you can see that some of the trial area was severely damaged this winter; this was likely desiccation (winter drought) with some extreme low temperatures and snow mold thrown in here and there.
What did we find out?
The damage was very location specific, and based on early observations, had little to do with the genetics of the cultivars in the trial. If there were some consistent difference between cultivars, we’d see winter kill differences between adjacent plots, but that was not the case.
What should you do about it?
Don’t plant a mostly perennial ryegrass lawn in Minnesota or other places with tough winters (we knew this, some of you knew this, others of you will learn the hard way and eventually know this).
Stop 4: Perennial ryegrass turfgrass breeding plots
What are you looking at?
This trial represents years of selecting perennial ryegrasses for winter stress tolerance. Until now, it looked like we had done a pretty good job. These plots survived the last several winters relatively unscathed with most damage from snow mold disease, which is a very common problem on many turfgrasses.
What did we find out?
We’ve got a lot of work to do. You can see that much like the NTEP trial above, the winter kill was very location specific, and based on the slightly raised elevation in the middle of the trial area, this was likely all due to desiccation. To be fair, we have never focused our selections on desiccation; most of our work evaluates tolerance to extremely low temperatures. Occasional dry winters might lead to a shift in focus for us.
What should you do about it?
Don’t try breeding perennial ryegrass for winter hardiness at home (you already knew this, we might need to know this).
That ends our winter damage tour. Time to get back to work!