Answer: According to Warren Schultz's book, The Chemical-Free Lawn, the ideal mowing height for bluegrass and tall fescue is 2-1/2" during cool weather or in shade, 3"-4" during hot summer weather, and 1-1/2" to 2" for a final mow at season's end. Perhaps this height is recommended during the spring to keep these grasses from going to seed. I don't know enough of the details of grass physiology to tell you what stimulates flowering in different species, but I'll bet a turf specialist at your state extension office (502-227-5905) can answer that for you. Did mowing at 2-1/2" to 3" not shade the weeds enough, and are the weeds really a problem in terms of competition? There may be other factors other than sun exposure that are encouraging weed growth, so I suggest discussing this with your extension specialist, too. Good luck!
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