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.
Ecballium Ecballium is a genus of flowering plants in the family Cucurbitaceae containing a single species, Ecballium elaterium, also called the squirting cucumber or exploding cucumber (but not to be confused with "Cyclanthera explodens"). It gets its unusual name from the fact that, when ripe, it squirts a stream of mucilaginous liquid containing its seeds, which can be seen with the naked eye. It is thus considered to have rapid plant movement.