Growing netherwart help

I'm trying to grow some netherwart and having some problems. According to the wiki you just have to plant it on soulsand and wait and no environmental factors matter. That doesn't seem to be working for me though.

I am working on a desert fortress in my current survival world and had made a trip to the nether to gather some wart for brewing and decided to grow a bit while I was working. I just stuck a half dozen blocks of soulsand on the ground and planted some wart on it and went back to working.

It's been several hours and I am not out of the area at all just on the other side of the building but when I go back to check none of the wart has grown at all. Help?
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Aww that's no good. I assume I have to be actually in the nether for growth to occur as well?
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Time magazine's Man of the Year in 2006! Really. Google it if you don't believe me.