Ericales

Ericales, rhododendron order of flowering plants, containing 22 families, 346 genera, and more than 12,000 species.

The relationships of the order are unclear. Together with Cornales, it is placed as a basal asterid in the Angiosperm Phylogeny Group IV (APG IV) botanical classification system (see angiosperm). The families included in it have previously been placed in several other orders, including the now defunct Theales. The circumscription of the order and its placement in the asterids are something of a surprise, although both are well supported by morphological and molecular data.

Morphologically, the order is rather generalized and unspecialized for the asterids. Most members have at least weakly fused petals and radially symmetric flowers, a superior 3- or 5-locular ovary, and 5 or 10 (sometimes more) stamens that are often borne free of the petals. The fruit is most often a capsule, and the seed coat is usually thin. Iridoids, distinctive chemicals perhaps involved in protection of the plant against herbivores, are scattered through the order.

Molecular studies suggest that there are eight family groupings in Ericales, plus one isolated family (Theaceae). The Ericaceae group contains Ericaceae, Clethraceae, and Cyrillaceae. The Balsaminaceae group contains Balsaminaceae, Marcgraviaceae, and Tetrameristaceae (including Pelliciera). The Polemoniaceae group contains Polemoniaceae and Fouquieriaceae. The Pentaphylacaceae group contains Pentaphylacaceae (including the former Ternstroemiaceae) and Sladeniaceae. The Styracaceae group contains Styracaceae, Symplocaceae, and Diapensiaceae. The Lecythidaceae group includes only Lecythidaceae. The Primulaceae group contains Primulaceae, Sapotaceae, and Ebenaceae. The Sarraceniaceae group contains Sarraceniaceae, Actinidiaceae, and Roridulaceae.