Note that Carpentaria should not be confused with the similarly spelled Carpenteria, a genus of shrubs in the family Hydrangeaceae native to California.
In addition, the genus Pottingeria is sometimes included in Hydrangeaceae, while others treat it in either Balanophoraceae, or in its own family Pottingeriaceae.
Molecular data suggest that there are four clades within the Cornales: Cornus-Alangium, nyssoids-mastixioids, Hydrangeaceae-Loasaceae, and Grubbia-Curtisia, with Hydrostachyaceae in an uncertain position, possibly basal.
Umbelliferone occurs in many familiar plants from the Apiaceae (Umbelliferae) family such as carrot, coriander and garden angelica, as well as in plants from other families, such as the mouse-ear hawkweed (Hieracium pilosella, Asteraceae) or the bigleaf hydrangea (Hydrangea macrophylla, Hydrangeaceae, under the name hydrangine).