In the desert southwest, bermudagrass goes dormant for 6-10 weeks, typically from mid-December through the end of February, although this year many courses saw the color of their bermudagrass decline near Thanksgiving. During the dormancy period, bermudagrass growth ceases and the plant loses its green color. Golf courses often seed ryegrass prior to the dormancy period, as it grows best in cooler weather into the October bermudagrass canopy. In order to successfully grow an entirely new grass through the winter and spring months, courses in the Southwest must close to have the opportunity to slow the growth of the bermuda, open the grass canopy to better accept seed, apply relatively heavy ryegrass seed rates, and water frequently to expedite seed germination and survival.
In Florida, temperatures in most years do not dip low enough for the bermudagrass to enter the dormancy stage. As a guideline, bermudagrass loses its chlorophyll (green color) as night time temperatures remain below 50° F. Courses either don’t overseed, or apply seed at low rates to enhance winter color. In this environment, course closure is unnecessary because they do not need to slow the bermudagrass growth and prepare a seed bed. In fact, they want to enhance bermudagrass growth and color for improved winter playing conditions and aesthetics.
The response to the second question is a resounding yes! Late fall fertilization with nitrogen and iron maintains bermudagrass color later into the winter and expedites spring green-up. Furthermore, painting greens, tees and even fairways gains momentum in the Southwest and serves as an excellent strategy to offer green color. Turf paints also raise surface temperatures, which shortens the dormancy period. Although it may take years for the golfing public to change their perception of the non-overseeded golf course, this practice is far more sustainable than growing-in a new seed crop each fall. In addition, non-overseeding is more environmentally friendly, and golfers appreciate longer drives from the roll!
Additional reading on this topic
Overseeding Roundup http://www.usga.org/course_care/regional_updates/regional_reports/southwest/Overseeding-Roundup---November-2008/