Nether Wart

Nether Wart is a plant grown in The Nether. It can be found within Nether fortresses on Soul Sand. 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
When left alone, Nether Wart planted in Soul Sand will grow through three distinct stages. Nether Wart does not react to bonemeal. Nether Wart only grows in the Nether on Soul Sand. Nether Wart has a 0.00407% chance of growing to the next stage every 1/20th of a second in Minecraft. This doesn't seem like much but given a few minutes you should notice its growth.

As of 1.0.0, Nether Wart can only be grown in the nether. It is advisable to do any 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.

Harvesting
There are three visual stages of development. During the first two stages, it will yield one Nether Wart. On the final, largest stage, breaking Nether Wart will produce 2-4.

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.
 * Nether Wart only grows in The Nether.