A healthy garden is an easy-to-maintain garden and a prerequisite is a balance through biodiversity - birds, small animals, insects and worms are nature's gardeners. Many animals and insects are specialized in certain types of plants and cultivated garden varieties may be impossible for, for example, a bumblebee to suck nectar from due to shape and hybridization. The garden therefore needs native plants and there are so many beautiful examples that we should grow more of in our gardens - sedges, meadow flowers, grasses and not least beautiful trees such as pine, birch and rowan. Leaves, dead wood and some weeds are also good for biodiversity so clean less and enjoy more :D