I filled my raised garden bed with Kellogg's raised bed and potting mix and have planted my vegetables (plants, not seeds). I've read that it's best to add a layer of mulch on top but this brand of soil already has mulch mixed in. Should I still add an extra layer of mulch on top?
There are other benefits to mulching. The layer of mulch on top is meant primarily to do two things; it should be applied when the soil beneath is already moist, when it will help to stop the soil drying out too quickly, and if the layer is 2 inches or more deep (but not sitting against the stems of your plants), to suppress or discourage weed growth. Over time, assuming the mulch is organic and not inorganic (stones or pea shingle) it will decompose and add humus to the soil, which is beneficial for ongoing soil fertility.