When will a plant be considered a weed? Experts have a simple answer: when the undesirable qualities outweigh (,) the good qualities. Crops generally produce several hundred seeds from each plant. By comparison, each weed plant can produce tens or even hundreds of thousands of seeds. And some buried seeds can survive up to forty years or even longer. Eradicating weeds means that you have to remove all the seeds and roots so the weeds will die completely. But birds or the wind can reintroduce them to the land. A common way to deal with weeds is to control them enough so that the land can be used for planting. Experts suggest using more methods to deal with weeds. Chemical weed killers or natural treatments like corn gluten   can suppress weed growth. Bill Curran is a professor of weed science. He says the most efficient method for suppressing weeds is dense planting. Dense planting of a crop can also act as a natural control. A dense and competitive crop that quickly shades the soil will help suppress many weeds. The weed seeds need light to grow, so cutting off sunlight will reduce weed growth. Other controls include turning over the soil, pulling the weeds or covering them with mulch   made of wood, garden waste or other materials. But even mulch has its limits. Natural resource specialists point out that weeds can be transported in mulch. This is also true of soil, grain, hay and animals. Yet animals like sheep or goats eat weeds, so they can provide a biological control. Insects and other organisms can also act as biological controls. Preventing the spread of weeds is an important part of weed management. Farm vehicles should be kept out of areas with weeds. If that is not possible, then clean off the equipment and your shoes when leaving. Some people bum weeds or bury them deep. Experts say the economical way is to make organically rich compost  . On the one hand, the process produces heat which can kill many weed seeds. On the other hand, the compost can be added to the soil to help plants grow. How does dense planting affect weeds?
The crops grow stronger than weeds. The crops grow deeper in the soil. The crops block sunlight the weed seeds need. The crops compete with weeds for shade.