Black plastic is an excellent mulch for the vegetable garden. The edges of the plastic are placed in trenches and covered with soil. Plants or seeds are set in holes made in the plastic. Black plastic controls weeds, but it also increases soil temperatures in the spring. Warmer soil temperatures promote plant growth and early yields of warm-season vegetables.
Black plastic is a poor mulch for landscape plantings.
Plastics can trap excessive amounts of water in the soil during wet weather, damaging the roots of trees and shrubs. Landscape mats, however, can be used around trees and shrubs as these materials allow water and air to pass through them. The landscape mats should be placed on the ground and then covered with wood chips or shredded bark. Herbicides can be used to help control weeds in the home garden. Cultivation, hand pulling, and mulches should be considered the primary means of weed control.