In the eternal battle against garden weeds, humankind has employed inventiveness and technological know-how to fend off plants that grow where they're not wanted. In this context, landscape fabric and mulches are not extras; they are replacements for the native plants and insulating layers of decaying organic matter taken from the soil of prairies and forest under stories.
Landscape cloth is a manufactured material or geotextile laid on top of soil by gardeners and landscapers to protect plantings. Mulch is a shredded organic or man-made material laid on the surface of soil or on top of landscape cloth. Several inches of mulch are applied around trees and specimens as well as in gardens. Weeds that grow through these materials are weak-stemmed and easy to pull.
Gardeners employ these ground coverings to retard the growth of weeds and maintain moisture in soil. Geotextiles hold soil in place and keep soil and mulch from intermingling. Mulch shelters plant and tree roots from hot summer sun and frigid winter winds. Mulch may be decorative; landscape cloth comes in several colors, but its basic purpose is as soil control and weed barrier.
The first landscape cloth was made of nylon; today's gardener's cloth is made of polyester, polypropylene or burlap. Fabrics are spunbond, needle-punched or woven to provide varying degrees of permeability and aeration. Specialized landscape fabrics are descended from geotextiles that retain soil or act as underlayment for construction.
Sawdust, hay, pine needles, grass, leaves and peat moss may be composted to make organic mulches. Wood, composted, shredded or chipped, is popular and widely available. Shredded tires are recycled to make mulch for play yards and landscaping. Cover crops like clover, rye or legumes, also called "green manures," are used to mulch fallow gardens and improve soil nitrogen.
Neither landscape nor mulch is a permanent solution or stops the growth of weeds completely. Seeds dropped by birds, carried by squirrels and deposited by soil-dwelling creatures will grow in or through both media. Both media wear out; organic mulch will decompose and become soil compost and landscape cloth will eventually degrade, especially if it is exposed to sunlight.
Two materials, gravel and plastic sheeting, may be suggested as weed barriers. Gravel works into the soil and is difficult to keep attractive. Since most decorative gravel is limestone, it may affect the acidity of the soil underneath even if it is laid over landscape cloth. Plastic sheeting seals off soil, overheating it and denying light, water and air to ornamentals and vegetables as well as weeds.