Colloquial term (also weeds) for various plants that occur as spontaneous accompanying vegetation. They are not deliberately cultivated, but arise from the seed potential of the soil or via seed flight. The criterion for "weeds" is that such plants enter into unwanted competition with a deliberately cultivated crop plant in terms of nutrients, water and light. By nature there are no weeds, even a vine in a rose bed is undesirable. Common weeds in viticulture are field mustard, field bindweed, amaranth, thistle species, common couch grass, common fumitory, shepherd's purse, knotweed species, dandelion, arrow cress, black nightshade, chickweed and willowherb. But these can also occur as medicinal herbs or indicator plants. The presence of the latter gives an indication of soil type and condition. These are, for example, sorrel (acid soil), black nightshade (humus-rich, loose soil) and chickweed (good nitrogen supply).