Herbicides are safe and effective if you follow the directions, but many folks never read the label. They often use too much and spray on a windy day. The herbicide drifts into the landscape and damages other plants. Mulches can be a safer alternative, but they have their downside too. Stone mulches create an environment often too hot for the plants.
Plastics look unsightly.
Wood chips are attractive and rot slowly, adding valuable organic matter to the soil. They keep the soil cool and moist, but mice living in the mulch in winter can chew the bark and kill your trees. Keep the wood chips a couple inches away from the trunk. String trimmers are popular and easy to use. They do a good job but can severely damage the tree when wielded by zealots.