Spring and Fall Color of Zoysiagrasses and Associated Freeze Tolerance.

 

Extended fall color and early spring green up of zoysiagrass would be commercially preferable.  Color retention in autumn, however, has been associated with poorer freeze tolerance in warm-season grasses.  Our objective was to evaluate zoysiagrass color in fall and spring, and determine potential relationships with freeze tolerance.  Eighteen experimental progeny, resulting from crosses between Zoysia japonica x Z. matrella, Meyer, and DALZ 0102, were maintained under golf course fairway conditions in 0.6 by 0.6 m plots. Color was determined weekly for 6 consecutive weeks in each season using a Nikon D100 AF LR 28:105 mm camera mounted at 1.2 meters above the ground. Images were analyzed using Sigma Scan Pro 5 under a hue threshold of 30 to 100, and saturation of 0 to 100.  Ten progeny were also subjected to freeze tolerance evaluation.  Plugs were sampled from the field in December and February and subjected to 4 (control), -10, -12, -14, -16, and -18 C.  After freezing, grasses were evaluated for survival by counting the number of tillers.  Analysis of variance was used to separate means of progeny color.  Correlation analysis was performed to determine potential relationships between fall or spring color, and LT₅₀ (the temperature killing 50% of tillers compared to the control).  In mid-April 2007, green color ranged from 8 to 68% for progeny, and was 60% for Meyer.  In mid-November, 2007 color ranged from 38 to 59% and was 38% for Meyer; in 2008, the range in green color was 4 to 24% and 6% for Meyer. Color on 25 October 2007 was correlated with color on 28 April 2008.  Hence, longer fall color retention did not slow spring green up.  Color in April, 2008 was correlated (r = -0.72) with LT₅₀ in February 2008, indicating that hardier progeny generally exhibited earlier spring green up.