The lone voice of horticultural reason
“Lawns should be fertilized in early spring”
In the north (USDA Zones 2-5): wrong. Research by the University of Minnesota shows that northern lawns actually suffer somewhat from early spring fertilization. Jolting your grass awake too early—when soil is still cool—stresses grass plants and causes them to perform poorer when faced with the heat to come later on. In the north, you should NOT fertilize your lawn four times, as the major lawn fertilizer companies try to tell you. Two (late May and mid-October) is adequate, three (late May, mid-July, and mid-October) is plenty.
Wait until late May/early June. If you fertilized your lawn in the fall, your grass is just fine right now, and should be allowed to become more active by the increase in soil temperature and rising angle of the sun, before giving it another dose of drugs, organic or synthetic.
The Renegade Gardener