There was an article in the most recent Golf Course Management that the out of play areas were not overseed on purpose-to save money.
The bunker surrounds were not overseed on purpose as well-This gives a great, defined look and also cuts back on the edging/fly mowing of the bunkers during the winter season with ryegrass. Those edges are seeded with a drop seeder along a specific line. The inside areas that you see dormant, have a preemergent applied to them, so no ryegrass will establish. I'm sure that they touched up the bunker faces within the last month for any "renagade ryegrass" that popped up.
Tony Nysse
Asst. Supt.
Colonial CC
Ft. Worth, TX