Late August through mid October is the ideal time for lawn rejuvenation in our transition zone. Wait until after a rain to core-aerate or verti-slice the cool season turf grass areas. This way, the soil is soft enough for the machine to penetrate 1/2″ to 1″ deep for the seed prep work. Soil to seed contact is the name of the game. Seeds are shaped like footballs, chances of germination are slim lying on top of hard ground. Even existing lawns benefit from core-aeration. Last year at the State of Maryland Dept of Agriculture Re-Certification class, Dr. Turner, the turf “guru”, spoke on this very topic. He indicated, while in the past, we often regarded core-aeration as a turf grass “up sell” program, the University of MD turf grass test plots showed an increased resistance to fungal pathogens where the grass had been core-aerated. So now, in addition to thicker turf, more weed control, less erosion and less compaction, core-aerating and overseeding actually increase fungal resistance. In this transition zone, overseeding with turf-type tall fescue is recommended. Fertilization should be done in the fall once every 30 days at a rate of 1/3 to 1/2lb of N per 1000 square feet, per recent MD State recommendations. Turf really benefits from multiple feedings in the fall because you are feeding additional new grass plant tillers that the plant has put out to capture more light. With long days in the spring, the turf produces vertical shoot growth. Feeding at his time creates excessive vertical leaf blade growth and necessitates more lawn cutting. No weed control materials should be applied now, wait until November or the spring.