Q: Typically I aerate, fertilize, and apply a long-lasting weed control to my lawn. Do you think the effects of each activity would be less than optimal if they are done too close together? 

A: I think this is fine for a spring sequence, with a small wait between the last two. Aerate the lawn first, which gives the grass roots good growing conditions. Soon afterward, apply fertilizer to stimulate strong root and shoot growth. Wait until after a rain or irrigation and put down the weed killer. If you’ve chosen your weed control product correctly, the newly emerged weeds will take up the herbicide and will die quickly.