When can you fertilize after Overseeding on an established lawn in spring.
Stearns County Minnesota
This is what the U recommends:
Late summer and fall are the principal times of year to fertilize lawns (Table 6). This is contrary to the traditional springtime application. Some advantages of fall rather than early spring applications are shown in Table 9. Early spring applications of nitrogen cause a surge of top growth in the plants, which makes the lawn look nice in the spring but depletes the plants’ energy reserves. Consequently, when summer stress periods occur, plants are weaker and less able to survive. Applying fertilizer in late August or early September will provide the plant with adequate nutrition to overcome any summer stresses.
See this link for more information:http://www.extension.umn.edu/garden/turfgrass/fertilizers/fertilizing-lawns/index.html and http://www.extension.umn.edu/garden/landscaping/maint/calendar.htm