If you want healthier plants and want to maximise your time enjoying the garden rather than maintain it then effective mulching is your answer. Adding organic mulch (such as wood, bark chips, grass clippings or leaves) over your garden improves soil moisture, minimises erosion, insulates the plant roots from high temperatures, suppresses weed germination and growth. Over time its breakdown (or composting) will also release invaluable nutrients improving soil structure and soil micro-organism activity and in turn plant health and vigour.
There are certain rules to generally follow when adding organic mulch and they are to evenly apply up to 75mm in thickness and avoid placing right at the base of plants to avoid the incidence of rot and disease. Be mindful also that depending on what type you choose it may affect your soil pH and how quickly it will decompose. Adding freshly sourced wood chips from arborists or coarse bark mulch can cause nitrogen draw-down as it slowly decomposes causing nutrient stress. So unless your mulch is composted then to boost soil microbial activity and get your garden humming try to add some nitrogen-rich fertiliser such as blood & bone, manure or organic matter such as sugar-cane or lucerne before your mulch layer.