The dendrometers presented here are used to determine the circumference, radius or diameter of plants. It has long been the case that not only trees are measured, despite the actual meaning of the word (tree measuring device). Modern dendrometers are becoming ever smaller, lighter and more accurate, which makes them suitable for an ever larger range of applications. For example special dendrometers can also be deployed for agricultural crops and fruits. Electronic dendrometers used in combination with data loggers permit the recording of entire hydrographs of the plant diameter over days, months or years so as to be able to make statements about the growth and conduct of the plants and the influence of correlating environmental factors.