Nether Wart

Nether Wart is a plant grown in The Nether. It can be found within Nether fortresses on Soul Sand - it currently does not spawn on any other blocks and will not respawn when taken from fortresses. Nether Wart in inventory can be placed onto Soul Sand by right-clicking (as if it were a seed), where it will grow.

Growth & Growing Conditions
Nether Wart can only be planted on Soul Sand. Like many other plants, it will uproot if it isn't in light level 8+, or a place that receives level 8+ sunlight during the day. In the Nether, this rule doesn't apply unless the Nether Wart is planted below a natural vein of glowstone or lava source block (this is probably a bug).

When planted in the Nether, each plant will grow through three distinct stages in a similar fashion to wheat, though the middle two stages have the same appearance (this can be verified by using a BUD switch to detect the stage transitions). The duration of each stage is random, with no upper or lower limit, but the average duration is about 3 minutes and 30 seconds.

Nether Wart can be planted outside the Nether, but it will not grow. Factors such as light level and proximity to lava or fire do not affect the growth rate. Nether Wart will only grow when its chunk is loaded. It is not affected by bone meal.

Because Nether Wart grows rather slowly, large farms are recommended to maintain an abundant supply. A great deal of time must be spent in the Nether to give the Nether Wart time to grow. One way to alleviate this is to do potion brewing in the Nether so that the Nether Wart will keep growing and there will hopefully be enough Nether Wart grown for when you need more Awkward Potions. However, potion brewing in the Nether presents the logistical problem of keeping a supply of water, which can be either brought as needed, or kept in cauldrons or filled bottles.

Harvesting
Nether Wart is ready to harvest when it reaches its third visual stage. Breaking a full grown Nether Wart yields 2 to 5 Nether Wart seeds. Breaking it before it's fully grown yields only a single seed.

Trivia

 * Nether Wart will not break when stepped on, unlike Wheat crops, nor will Ghast fireballs destroy them (though, fire caused by the fireballs will).
 * It makes the same sound as stone when destroyed.
 * In the code, Nether Wart is called "netherStalk" for the block and "netherStalkSeeds" for the item.
 * There appears to be a glitch where if a nether wart is placed in a location under or on a naturally generated glowstone or lava, it would break off when it is updated if it has under 8 light level no matter the distance or whether the nether wart is blocked off from the said blocks or not.