Remnants of medieval field patterns, called “pluzina” in the Czech Republic, are valuable historical landscapes, similar in character to the bocage landscapes typical for some countries in Western Europe. The original historical pattern of fields and meadows has persisted due to the stabilizing network of hedgerows. As in other countries, the development of these medieval fields in recent decades for intensive agriculture or residential purposes has led to their dramatic decline. This study evaluates the dynamics of the development of medieval pluzina hedgerows during the second half of the 20th century in the Plzen Region of the Czech Republic, using three datasets from 1840, 1950 and 2005. Between 1950 and 2005, 341 out of 483 hedgerows disappeared in the study areas, and the total length of the hedgerows decreased by 71%. At the same time, the average hedgerow width increased from 7.2 m in 1950 to 13.1 m in 2005. The study further tests the influence of three natural factors (natural soil fertility, slope gradient and aspect) and of historical (1950) and current (2005) land uses on the disappearance of hedgerows. The most significant factor that has contributed to the disappearance of hedgerows is the current land use in adjacent areas, grassland being by far the most conducive to the persistence of pluzinas. In addition, current land use has significantly influenced the hedgerow dynamics when assessed in interactions with slope gradient and with historical land use. The results of the study further show a significant influence of natural soil fertility. Our findings confirm two main trends which lead to the disappearance of medieval land use systems. Extensification of agricultural land leads to its abandonment and to afforestation of fields adjacent to the hedgerows as a result of spontaneous succession. On the other hand, intensification means that land adjacent to the hedgerow is used as arable land and gradual expansion leads to field enlargement, hedgerow removal and consequently to the disappearance of the entire medieval field patterns. The paper also discusses the principles of conservation and restoration of these valuable historical landscapes.