Perennial ryegrass growing degree days (GDD)
Perennial ryegrass GDDs will be tracked during the 2025 growing season with comparisons to the previous seven years. The accumulation of GDDs will begin after the snow has melted from the perennial ryegrass fields and continue through swathing. A base temperature of 32 °F will be used for perennial ryegrass GDD model.
- Year-to-date GDD = 502 (Table 1)
- GDD last week (May 5 - 11) = 191 or 27.3/day; long-term average = 124 or 17.7/day
- GDD forecast for the next 10 days = 245 or 24.5/day
- Average GDD accumulation for the third week of May = 151 or 21.6/day
- The 10-day forecast suggests slightly above average temps for the third week of May. Projected GDD is 24.5/day compared to the long-term average of 21.6/day
| Year | 2025 | 2024 | 2023 | 2022 | 2021 | 2020 | 2019 | 2018 | 2025 vs. 2024 |
|---|---|---|---|---|---|---|---|---|---|
| March | 0 | 0 | 0 | 0 | 131 | 30 | 0 | 0 | 0 |
| April | 229 | 296 | 93 | 95 | 236 | 183 | 211 | 184 | -67 |
| May | 273* | 653 | 959 | 649 | 640 | 600 | 548 | 815 | N/A |
| June | N/A | 859 | 1,064 | 959 | 1,007 | 995 | 919 | 1,007 | N/A |
| July | N/A | 1,119 | 985 | 1,104 | 1,174 | 1,179 | 1,067 | 1,100 | N/A |
| Total | N/A | 2,927 | 3,101 | 2,807 | 3,188 | 2,987 | 2,745 | 3,106 | N/A |
General crop condition
Perennial ryegrass winter survival reports from area fields range from a full stand to ones with significant gaps. Lack of snow cover, alternating warm and cold temperatures after snow melt, wheat stubble height, cover crop with late summer seeding and ponded water seem to be important factors in ryegrass winter survivability in 2025.
U of MN and MN Turf Seed Council Summer Field Day
The annual Grass Seed Field Day is scheduled for June 26th. Additional details will follow in future newsletters.
Crop management
The U of MN conducts a perennial ryegrass winter hardiness trial each year. The objective of this trial is to evaluate perennial ryegrass genetics and determine genetic differences in perennial ryegrass ability to survive the winter. Ryegrass plants that die over the winter fit under the winterkill umbrella. However, a better term could be spring kill as observations suggest the environmental conditions after the snow has melted to when ryegrass breaks dormancy is the most likely time for plant leaf and crown desiccation and plant death. A ryegrass winter hardiness trial with 16 entries was seeded on 9/11/24 at Roseau into fallow conditions which would be considered a worst case scenario. Ratings taken on 5/8/25 indicate a high degree of winter injury on most ryegrass lines. The visual rating scale used:
- 1= dead plants
- 9= healthy green vigorous plants.
The range in visual injury was 1 to 4.5 for the various perennial ryegrass entries. The average winter injury from the sixteen varieties in this trial averaged of 2.4. The data from this winter hardiness trial suggests that the 2025 season has potential for significant winter kill.
The assessment of perennial ryegrass stands in production fields that have experienced winterkill from environmental stress can be a challenge. Typically, the winterkilled areas are not uniform, rather irregular patterns in the field. One method to assess stands is the use of a grid to determine the presence or absence of plants. The grid frame used to collect the following data had a total area of 30 inches x 30 inches and each individual square was 6 x 7.5 inches. The collected data indicates that ryegrass stands of 56 and 73% of a full stand produced similar ryegrass seed yields. However, ryegrass stands of 39% of a full stand produced 553# of ryegrass seed compared to over 1,000 pounds/acre for 56 and 73% stand.
Pest management
The yellow flower of common dandelion has been observed in area fields. In addition, winter annual weeds are growing well, and some species are close to bolting. If a broadleaf herbicide was not applied last fall ryegrass these fields should be scouted to determine the infestation levels of winter annual weeds. With the increased soil temperatures, the cool season annual weeds are beginning to emerge from the soil. Volunteer canola, wild mustard, common lambsquarters and smartweed species are examples of cool season broadleaves that one of the first weed species to emerge from the soil. Annual bluegrass has emerged and is growing well. Warm season weeds have yet to emerge and will take additional heat to promote germination. Redroot pigweed and tall waterhemp are examples of warm season broadleaf weeds. The foxtail species and barnyardgrass are examples of warm season grasses and will take more heat to stimulate germination.
Next week’s newsletter will be released on May 20.