COLD TOLERANCE: Which has better cold hardiness, Tifdwarf or Tifgreen (328)?  Tampa area

ANSWER: There appers to be no clearcut difference.  I have scanned thousands of publications, and can find only one side-by-side comparison of the two grasses for cold (Ibitayo et.al. 1981.   Cold hardiness of bermudagrass and Paspalum vaginatum Sw. Hort Science 16:683-684).  These are low temperature killing points (Centigrade) determined in Colorado in 1978:

	Oct 18	Nov 15	Dec 14	Jan 13
Tifdwarf	-3	-5	-11	-11
Tifgreen	-2	-6	-9	-11

Tifdwarf purples considerably when air temperatures drop to 13 C (54 degrees Fahrenheit).  The purpling appears to be a normal and healthy response in which Tifdwarf manufacturers anthocyanin, a purple pigment.  Dr. James Beard has described this phenomenon as winter chill injury, but it should not be confused with winter injury, as the two are not related.  The purpling of Tifdwarf can last for as little as a couple days, as new green leaves are produced immediately if temperatures increase.   If temperatures descend, then the purpling is just the first progression towards dormancy, which will to some degree protect the plant.  The fact that both Tifdwarf and Tifgreen had lower killing points in December and January, compared with October and November, shows that dormancy was eventually achieved, and that neither grass had superior cold hardiness.