The basis of this experimental plant was a root found by a Brotherhood field scribe at the mouth of a river, and displayed unique chemical properties, prompting the scribe to graft it onto a hardier stock for further testing and hybridization.
The result was a leafy plant with thick roots, and after being determined safe to ingest, it was brewed into "an oddly good tea." Soon after, other samples of the plant began to exhibit a form of bioluminescence. The scribe deduced that the leaf must have restorative properties due to how healthy they felt, but other scribes suggested that the tea should no longer be brewed and that the plant is addictive in nature.
The plant is a purple bioluminescent article with thick roots. It has been named "Glowleaf" by one of the senior scribes aboard the Prydwen. They were using it to make tea and wound up becoming addicted to the substance. After the addiction began to make them agitated with their fellow scribes, the scribe was reassigned.
Three can be taken from the biolab area on the Prydwen.
A single plant can be found on the Island, straight west of the Eden Meadows Cinemas map marker. It is located next to an aster and two garden gnomes under a parasol. Since the plant is partially buried underground, it can only be harvested while being crouched.
This item has no addiction effect.
In Survival mode, the item has no food value (similar to wild plants and fungi) and provides its Health buff regardless of whether the player character is Well Fed.
If taken, a Prydwen Mister Gutsy will express its displeasure with the player character for touching the experiments.
Behind the scenes
Despite fan theories stating that the plant's similarity to nirnroot proves the Elder Scrolls and Fallout take place in the same universe, Pete Hines denied any connection.
Plant location on the Island
Using clipping commands, the planter can be clearly viewed
↑Pete Hines: "I haven't the foggiest of notions how anybody could make the leap that they are in fact part of the same thing. We made Elder Scrolls, and a completely different developer and publisher came up with Fallout, which we then acquired. [...] I don't think there's any universe in which those universes are in the same universe. That's not a thing." (Gamespot interview)