How tall are you letting the grass get before you mow? Or I guess the better question would be how much are you cutting off? I try to follow the 1/3 third rule of thumb and cut my Fescue at 2 1/2 inches when it reaches about 3 1/2 to 4 inches tall. The only time I've ever had clumps left by my mulching mower or had heavy build-up under the deck is when we'd had a lot of rain and the grass was really moist. The grass itself wasn't wet, it was just full of moisture internally because it had had plenty of water.

well it is MN. cool weather. i have mowed twice this season. 1st mow was 2 weeks ago. 2nd mow was monday? so about 8-10 days. mower has never really mulched good.

well, i did not look under deck on 1st mow. but i blew out the side so debris buildup should have been minimal? mowed 2nd time and checked deck and lots of crud. maybe it had more debris from last fall than i remember.

cleaned deck, sharpened blades. seems to be mulching ok. neighbor has newer toro rider. his yard looks awesome usually. yesterday he had a ton of debris. had to make perpendicular passes to chop up yard. his yard is lower than mine. catches my runoff i suppose. looks a little greener also.