The genus Hypericum contains approximately 500 species which are divided into 36 sections as described by botanist Norman Robson. This division into distinct sections is largely due to the fact that a genus-wide monograph was performed by Robson in 1977, which allowed for a comprehensive analysis of the genus's taxonomy. A phylogenetic study was more recently completed for the genus, which gave evidence to suggest that the genus Triadenum is a clade within Hypericum and that the genus Thornea is sister to Hypericum. In addition, the study found that about 60% of the sections of Hypericum are monophyletic.