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.
Echium italicum Echium italicum, the Italian viper's bugloss, Lady Campbell weed, or pale bugloss, is a species of plant from Boraginaceae family, that can be found in the Mediterranean Basin (especially in Italy, hence the name 'italicum') and, as an introduced species in the United States (for example in the state of Maryland).