SUB-ZERO™ boasts top 2% turf quality and top 3% color in fertilized NTEP locations in the North Central region (IA + MN). Distinctively the #1 performing perennial ryegrass blend for areas with slightly colder winters like IA, WI, ME, MI, & NE.

SUB-ZERO™ was designed specifically to be the undisputed #1 highest performing perennial ryegrass blend for areas like Iowa, Maine, Wisconsin, and much of Michigan and Nebraska and parts of Illinois.

Best for areas with an average January low between about 10º-15ºF.  Googling your city name with the word climate will usually list average January lows for your city.  For average January lows higher than 16º CHEAT CODE™ is likely to outperform SUB-ZERO™.

Note: for areas colder than ≈10° average January low, SR4750 PRG or KBG or Hard Fescue or Sheep Fescue may outperform SUB-ZERO™ blend.  A higher probability for the need to overseed in spring should be expected in areas with harder winters.

BLENDS HAVE BEEN RANKED BASED ON THE PERFORMANCE AVERAGE OF ALL PUBLISHED CULTIVARS INCLUDED IN THE BLEND.  DATA PULLED DIRECTLY FROM THE MOST RECENTLY CONCLUDED NTEP TRIAL (SEE IMAGES).

SUB-ZERO™ contains: Umpqua & Mystique (Perennial Ryegrass)

 

PRIMARY PERFORMANCE METRICS

TURF QUALITY (IOWA + MINNESOTA)

**  ICV WEIGHTED AVG  **

      SUB-ZERO™:  6.40 / 9.0

      Iconic*: 6.07 / 9.0

      Knorr Elite*:  6.05 / 9.0

      SS9000: 6.05 / 9.0

      5-Iron*: 6.01 / 9.0

      Fireball+Hatrick:  5.68 / 9.0

 

 

GENETIC COLOR (IOWA + MINNESOTA)

**  ICV WEIGHTED AVG  **

      SUB-ZERO™:  6.78 / 9.0

      Hatrick + Fireball: 6.36 / 9.0 ***

      SS9000:  6.31 / 9.0

      Iconic*: 6.24 / 9.0

      Knorr Elite*:  6.23 / 9.0

      5-Iron*:  6.17 / 9.0

*** note: the weakest genetics can thin which means more nitrogen per plant... color ratings of the cultivars with the lowest turf quality should be taken with a grain of salt since the color advantage may simply be correlative from the tendency to thin and die (which may bias more nitrogen per plant in the test plots for the very weakest cultivars)

 

SUPPLIMENTAL PERFORMANCE METRICS

Disease Score™ (Sum of NTEP tables 33-37)

**  ICV WEIGHTED AVG  **

      Iconic*:  Top 22%

      SUB-ZERO™:  Top 22%

      Knorr Elite*:  Top 23%

      5-Iron*:  Top 25%

      SS9000:  Top 32%

      Fireball+Hatrick:  Bottom 8%

Note: regional turf quality is usually a more accurate indicator of climate specific disease performance.  Diseases were tested in specific NTEP locations.

 

TRAFFIC & WEAR SCORE™

      5-Iron*: Top 15%

      Iconic*: Top 17%

      SS9000:  Top 17%

      Knorr Elite*:  Top 28%

      SUB-ZERO™:  Top 34%

      Fireball+Hatrick:  Bottom 16%

 

Percent Poa Annua After ≈ 5 Years

**  Context: NJ - NTEP 2021  **

      SS9000:  1.7%

      Iconic*:  1.7%

      5-IRON*:  2.0%

      SUB ZERO™:  3.3%

      Knorr Elite*:  3.6%

      Fireball+Hatrick:  20.9%

 

Divot Recovery (AKA: Self Repair, Context: KY)

      SUB-ZERO™:  Top 6%

          ** Mystique is slightly stoloniferous  **

      Iconic*:  Top 23%

      Knorr Elite*:  Top 29%

      5-Iron*:  Top 34%

      SS9000:  Top 46%

      Fireball+Hatrick:  Bottom 4%

 

Low Input Score™ (60% FROM UTAH DROUGHT TESTING)

**  See Specialty Performance Data spreadsheet for calculation  **

      Iconic*:  Top 8%

      SS9000:  Top 10%        

      5-Iron*:  Top 14%

      Knorr Elite*:  Top 17%

      SUB-ZERO™:  TOP 30%

      Fireball+Hatrick:  BOTTOM 32%

 

See images for recommended seed rates and seeding tips.

 

 

CAUTION: EVEN THE MOST COLD-TOLERANT PERENNIAL RYEGRASS IS NOT RECOMMENDED IN EXTREME COLD SUCH AS NORTH DAKOTA (UNLESS YOU'RE OK SEEDING IN SPRING EVERY YEAR).

MEHLICH-3 POTASSIUM ABOVE ≈120-140PPM MAY REDUCE PRG WINTER KILL RISK IN NOTABLY COLD AREAS.

 

 

 

Competitor blend performance averages are based on the following published cultivars (note: this cultivar list is not guaranteed to be up to date... last checked March 21st, 2026):

 

5-Iron (United Seeds): Apple 3GL, Fastball 3GL, Slugger 3GL, Stellar 4GL, Infusion* (JR-178 test name)

SS9000 (SeedSuperStore): Grand Slam GLD, Stellar 4GL, Slugger 3GL

Knorr Elite (Ryan Knorr's Website): Electra GLR, Paradox GLR, Pangea*

Iconic (United Seeds): Stellar 4GL, Slugger 3GL, Homerun LS, Torsion* (Torsion exempt from averaging due to no NTEP data)

 

*  The performance of one older cultivar in Knorr (Pangea) and one older cultivar in 5-Iron (Infusion, test name JR-178) has been translated by sorting the 2011-2014 NTEP trial data into a percentile among all cultivars in that trial on a trait by trait basis.  The rating of the cultivar at the same percentile in the newer trial was then assigned to the older cultivar trait by trait.  No deduction was made for ≈6 years of breeding so the translation is believed to be slightly generous.  These numbers are intended to estimate performance as accurately as possible but it should be considered an estimate only.  The slightly older infusion cultivar was exempt from averaging for 5-Iron and the slightly older Pangea cultivar was exempt from averaging for Knorr for the Low Input Score trait due to difficulty of translation.  The Torsion cultivar in Iconic LS was exempt from all averaging since no NTEP data is available.

 

 

Disclaimer: Seed-Boss makes no guarantee of performance in your climate or under your management practices.  If the grass seed does not germinate the buyer acknowledges improper seed to soil contact, improper soil moisture during germination phase, and/or inappropriate soil temperatures and agrees to not blame the seed (since seed was tested as good).

If you notice anything inaccurate or that could be improved for accuracy, please email us at SUPPORT@SEED-BOSS.COM.  Our aim is the highest degree of accuracy possible and that process includes peer review.