since the spike growth is in the standard 5e ranger spell list it should also be with solasta? i don't know the timing of it but i assume spike grown was not made when the base solasta game was released but later when the druid DLC was released. it could just be an oversight or TA does not want the ranger to have it for some reason? but at the very least those with the druid DLC should be able to have their ranger's get access to it.
yellow flower of courage