Oblivion:Nirnroot

thumb|left|Nirnroot
The ingredient Nirnroot comes from the "Nirnroot Plant", which can be found growing outside near water and indoors as a potted plant. It is a very noticeable, vibrant, greenish-blue plant with four large leaves that emits a quiet ringing noise. There are hundreds of locations where the plant can be found, but unlike every other plant in the game it does not regrow; each plant can only be harvested once. As a result, it is considered to be a rare plant. It cannot be duplicated in the Arch Mage's Enchanted Chest, or by scroll duplication or arrow duplication. It can, however, be duplicated using the Skull of Corruption.

The first time you harvest a Nirnroot plant, a new quest, Seeking Your Roots, will be added. To completely finish the quest you will have to collect 100 Nirnroot samples, though it's divided into smaller quests where you have to collect 10, 20, 30, and 40 roots, respectively.

Nirnroot's alchemy effects are all unique among Oblivion ingredients, and therefore cannot, in general, be used to create any poisons. Only a master alchemist can create a poison using Nirnroot, the result being a Drain Health poison. If the Shivering Isles expansion pack is installed, a new ingredient, Unrefined Greenmote, is added that also has Drain Health and Drain Fatigue effects, allowing poisons with those two effects to be created.

  
Ingredients
Normally there are no guaranteed samples of Nirnroot. The Deepscorn Hollow official plug-in, however, adds a single sample of Nirnroot sitting on a desk in the bedroom area of Deepscorn Bastion. Because this Nirnroot is, for some reason, designated as a food, this sample will respawn every three days. This is the only instance of Nirnroot in the game that respawns.

 
Plants
thumb|right|500 px|Locations of Nirnroot plants
In total, there are 306 Nirnroot plants in the game, with 263 found outside and 43 inside. One more can be found in the Wizard's Tower official plug-in, another in Battlehorn Castle and one respawning sample in Deepscorn Hollow, for a total of 309 when using official plug-ins.

Outdoor
The map to the right provides an overview of where each of the outdoor Nirnroot plants can be found. The   shows the exact locations of every plant in the game; zooming in to maximum will show all the plants in that area. A large image with all the outdoor Nirnroots can be found here.

The vast majority of plants are on the banks and tributaries of the Niben, with smaller, although not less dense concentrations on the coast west of Anvil, the coast south of Leyawiin, and the 'rainforest' east of Leyawiin. Less than a quarter of the plants can be found elsewhere.

Four of the Nirnroots are notable for being significantly larger than usual, i.e., almost as tall as a man. This is because the scale factor for each of these plants is set to be larger than one. They are identical to normal Nirnroot plants in all ways other than their size. The plants are located in the region between Skingrad and Kvatch, specifically at:
Two are on the shore of the pond east of Shardrock. Their scale factors are 1.87   and 1.67  
One is on the shore of the pond just southwest of Bleak Flats Cave, scale factor 1.85  
One is on the shore of the pond east of Shetcombe Farm, scale factor 1.77  
There are also 16 Nirnroot plants that are smaller than usual, although not enough to be remarkable.

Indoor
These are small plants that grow in flowerpots inside houses and buildings. Note that you can freely "steal" indoor Nirnroot without any repercussions, even if someone is watching you.

Anvil
Heinrich Oaken-Hull's Private Rooms (bedroom)
Anvil Castle: Private Quarters (Dairhill's apartment)
Lighthouse: Ulfgar Fog-Eye's House

Bravil
Andragil's House
City-Swimmer's House
Silverhome on the Water, 3rd Floor
Chapel Hall (room on the right)
Fighters Guild Second Floor (first room)
Bravil Wizard's Grotto (you can enter via a secret entrance in Castle Bravil. See the quest Arrow of Extrication)

Bruma
Baenlin's House (2nd floor)
Regner's House (downstairs)
Castle Bruma: Lord's Manor (Tolgan's apartment)

Cheydinhal
Mach-Na's Books (bedroom upstairs)
Cheydinhal Mages Guild Well (underwater, see Cheydinhal Recommendation)
Riverview (upstairs)

Chorrol
Casta Scribonia's House (upstairs)
Vilena Donton's House Third Floor

Imperial City
Arcane University
Arch-Mage's Quarters (you must complete the Mages Guild questline to legally take this one)
Mages Quarters (room on the right) (Access to the Arcane University needed)

Market District
Mystic Emporium Private Quarters
The Gilded Carafe
Imperial Prison Sewer
The North Tunnel (1st hall on the right when entered from North Exit)
Talos Plaza District
Samuel Bantien's Private Quarters
Temple District
Salomon Geonette's Private Quarters
Waterfront District
Marie Elena Captain's Cabin

Other places in Imperial City
South Watch Tower, (entrances from Temple District and Arboretum) Captain's Quarters (office of Hieronymus Lex, top of the tower)

Leyawiin
Ahdarji's House 2nd Floor West
Blackwood Company Hall (2nd Floor)
Blackwood Company Jeetum-Ze's Room (2nd Floor)
Margarte's House (room on the right)

Skingrad
Surilie Brothers' House (3rd floor)
Toutius Sextius' House (3rd floor)

Other
Border Watch: Border Watch Inn
Brindle Home: Torbal the Sufficient's House
Fort Cedrian: (1st zone)
Fort Roebeck: (1st zone)
Fort Grief: Hunter's Run (1st zone)
Hackdirt: Natch Pinder's House (upstairs)
Lord Rugdumph's Estate (upstairs)
Odiil Farm: (inside the farmhouse)
Pell's Gate: Shafaye's House
Smuggler's Cave
Veyond Cave: Veyond Black Waters (2nd zone)

Plug-in Specific Plants
Frostcrag Spire: Alchemy garden in the corner between the base of the "mossy rock" and the floor of the left garden (facing from the bedroom).
Battlehorn Castle: Behind the stuffed Wolf in the trophy room.
Deepscorn Hollow: A respawning Nirnroot sample on the desk in the bedroom (once you have purchased the bedroom area).

Notes
The word "Nirnroot" refers to Nirn, the planet on which the Elder Scrolls is set.
When searching for Nirnroots, it may be helpful to go into Options, then Audio, and turn the Master volume and the Effects volume all the way up and turn everything else down (voice volume doesn't really matter). This makes the distinctive chiming sound created by the Nirnroot much easier to detect and locate.
The reason Nirnroot doesn't regrow is because Nirnroot plants have a script that disables them. On PC, you can use console commands to re-enable them by clicking on it in the console before harvesting it, then harvesting it, and finally typing   into the console.