What type of category does Echium and Oxydendrum have in common?
Oxydendrum Sourwood or sorrel tree, Oxydendrum arboreum, is the sole species in the genus Oxydendrum, in the family Ericaceae. It is native to eastern North America, from southern Pennsylvania south to northwest Florida and west to southern Illinois; it is most common in the lower chain of the Appalachian Mountains. The tree is frequently seen as a component of oak-heath forests.
Danthonioideae Danthonioideae is a mainly southern hemisphere subfamily of grasses, containing the single tribe Danthonieae and three unplaced genera, with altogether roughly 300 species. It includes herbaceous to partially woody perennial or annual (less common) grasses that grow in open grasslands, shrublands, and woodlands. It belongs to the PACMAD clade of grasses, but unlike some other lineages in that clade, grasses in the Danthonioideae exclusively use the C photosynthetic pathway. Its sister group is the subfamily Chloridoideae.