I would say all along, but specifically befroe and while fruit appears, but it depends upon what kind of fertilizer you are using, for if slow acting then it should be worked into the soil early. This year I put some 40 lb. All-Purpose Fertilizer 10-10-10 in the hole before planting the plants that had been started indoors, then covered it with some dirt, and planted.
Weeks later I sprinkled some near the plants before rain, and a couple weeks later when I actually watered them (heavy rains about once a week meant I did not need to) I mixed some Miracle-Gro in the water.
Just some quick overhead shots of toms and butternut squash, thanks and glory be to God. The only real problems yet in this overcrowded city plot have been early blight on Goliath toms.
