If spring is cool, mulching warm season vegetables is a poor idea early in the growing season. Wait until soils have thoroughly warmed before applying mulch. This is particularly critical for pepper production. Peppers don’t produce well if mulch keeps soils cool. Wait until July to mulch with grass clippings or other mulches.
Note that mulch can be used now for selective uses such as germinating seeds. Both floating row cover fabric by itself or combined with dried grass clippings on top can be useful for starting small seeded vegetables that are shallowly planted. Remove floating row cover mulch after seeds germinate.
Not all vegetable plants like the same growing conditions. Heat-loving peppers, tomatoes, eggplants, and melons love black plastic mulch. Applied in early spring the plastic will raise soil temperatures and help warm the air around the plants. Install a sub-surface irrigation system beneath the plastic mulch. You might also consider removing the plastic in late July and replace with straw, newspaper or grass clippings.
Cool-weather crops such as broccoli and greens don’t want extra heat from a plastic mulch. They like straw, shredded leaves, paper mulch or newspaper. These mulches can lower soil temps by as much as 20-25 degrees.