During the past years, increased knowledge about the nutritional status of solitary trees has led to the development of soil and foliar analysis as a tool for the assessment of both chloride damage and nutrient deficiencies in The Netherlands. Data on threshold levels per tree species and element proportions are summarized. This enables the arborist to distinguish between various causes that exhibit similar symptoms (such as potassium deficiency, chloride damage and drought). The state of the art for the use of of soil and foliar analysis in arboriculture is briefly discussed and threshold values are presented.