People with green thumbs tend to be all-around green, often seizing opportunities to reuse everyday products in Earth-friendly ways. Cardboard is a favorite among gardeners for a variety of purposes. Some use pieces of flat cardboard to kneel on during grueling hours of weed-pulling and seed-planting.
Another gardening use for cardboard is sheet mulching, which is done to block and kill weeds and insulate plants during the frigid winter months. Gardeners recommend obtaining large pieces of cardboard and then laying them down on top of existing soil and weeds. Overlap the edges to keep the sun from penetrating through. The cardboard blocks sunlight from the weeds, preventing them from growing. You can also cut pieces of cardboard to fit around existing shrubs and plants, providing insulation to delicate greenery in the cold weather. Simply cover the cardboard with a couple of inches of mulch, wood chips or leaf litter and wait until spring. Over time, the cardboard will decompose and enhance the soil. Garden-friendly earthworms also appreciate the warmth the cardboard provides [source: San Francisco Gate]. Even weed and grass-filled flowerbeds can be turned into lovely plots of flowers using this time-tested method of gardening.