At present the early remains of weeds are a special field of research in palaeoethnobotany. These investigations result in fundamental knowledges about the early history of weeds, agriculture and the environment of the early farmers. Nowadays the remains of 300 weed species are known in Central Europe. In the analysis a lot of methodical problems must be considered, e.g. such points as the cause of presence (Präsenz) of a species, the value of their representative diaspores (Repräsentanz), the finding chance, the conditions of conservation in the sediment and the method of harvesting. On this platform one can get an exact knowledge about the species as idiochorophytes, archaeophytes or neophytes. The ecological evaluation of the prehistoric weed remains shows that many early weed species don't have special requirements for the qualities of the habitats. But apparently the early fields were neither wet nor dry. There are no indications of lack of nitrogen in the soils of early fields. After change in harvesting methods from spike harvesting to harvest near the ground during the Preroman Iron-Time and in the Middle Ages a lack of nutrient salts arose. Then a more intensive form of fertilizing must have started. Many of the very early weed species belong to the Chenopodietea-assoziations. But this is not an expression for the so-called Hackbau in the beginning of tillage in Central Europe. The advance of the Secalinetea-species resulted from the more intensive wintercrop-and especially winter-rye-culture during the Middle Ages. In 8 figures the finding places of 8 very typical weed species are shown.