The Caryophyllid clade or Caryophyllales sensu lato contains about 29 families grouped in two major clades (Fig. 9.1; Cuénoud et al.,2002; Brockington et al., 2009). A natural Caryophyllales (‘Centrospermae’) has been recognized for a long time, mainly on the basis of embryological and phytochemical characters (e.g. Mabry, 1977). Inclusion of molecular characters has increased the size of the order dramatically by adding carnivorous plant families (including Droseraceae and Nepenthaceae), knotweeds (Polygonaceae) and some halophytic groups (Frankeniaceae, Tamaricaceae and Plumbaginaceae). Except for carnivorous families, these taxa were often associated with Caryophyllales in the past. Whether these taxa should be grouped with core Caryophyllales or be separated within the Polygonales depends on a better resolution of phylogenetic relationships (e.g. Cuénoud et al., 2002; Brockington et al., 2009).

Core Caryophyllales have a number of floral features in common that clearly separate the clade from remaining core eudicots. Flowers are basically pentamerous and apetalous, with a derived insect-pollination syndrome. The ovary regularly has a free-central placentation by break-up of septa. Styles are typically separate or there are well-developed style branches. Ovules and seeds are characteristically curved (campylotrous) and the reserve tissue of seeds often contains perisperm. Nectaries are typically situated on the inner side of the stamens or stamen tube.

However, the addition of families previously thought to be unrelated alters the context in which to approach characters of the group. Members of Polygonales contain families where petals are present and others without (e.g. Polygonaceae, Nepenthaceae).