There already is sort of a feat for that, though I don't remember the name (Healer?). It basically boosts the use of Healing Kits. I've always sort of assumed the Healing Kit would take different forms for different classes or even subclasses - i.e., if a ranger or druid took it, it's more of the natural herbs and moss bandages, where a cleric of healing it's more like a medieval medical doctor's black-bag.
But the idea of a nature warrior knowing how to find special plants, moss, bark, mud-packs, etc. is a trope that goes beyond just LotR. But at the same time, I see where one might reasonably expect the concept to extend to barbarians and druids. In a class-based system like D&D, you're always going to run into instances where the need for balance and some niche preservation is going to conflict with "realism" and verisimilitude.
In this case, I think the spell-less Ranger fills in the gap between druid and barbarian. Druids draw directly from the magic inherent to nature (no need to actually rip-up a living plant to heal someone), and barbarians are in touch with their primal instincts and animal nature, but aren't necessarily that knowledgeable about nature in general.
The no-spells Ranger is very knowledgeable about nature, but particularly about natural applications, especially since, by definition, they can't rely on magic for said application. Again, druids probably also know about these applications, but are reluctant to utilize natural resources this way.
Also note, it's not that mundane of a skill, since it's much better than even the Healer Kit feat. It's non-magical in nature, but the Ranger obviously knows how to make his "bandages" much more effective.
