Is jarrin root found in some specific locations? I've pretty much exposed all locations on the map but other than being given some in a quest I've never come accross any. Thanks.

DB quest item.

Jarrin Root is not native to Skyrim iirc. As mentioned it is only used in a specific faction quest line.

Http://www.uesp.net/wiki/Skyrim:Jarrin_Root
What they said. But it doesn't make a whole lot of sense for it to be the ONLY one of its kind and yet at the same time for it to be SO common that during the
quest it is accepted (and ignored) by the NPC involved. Especially since it could just as easily have been done with Nirnroot and several other ingredients.

I think the person making the meal was more likely to be expecting unusual ingredients from The Gourmet, and wouldn't have wanted to look ignorant by questioning anything.

Yeah, and if I remember correctly, the Gourmet was bringing the rare ingredients with him from a different region, right?

Yeah, I think The Gourmet had trade secrets like Colonel Sanders, plus he was smuggled into the country by the secret police and confined indefinitely in a safe house, so lots of 'secret chef's business' going on with him... Who's going to question that authority???

They were worried that he might be bribed in to assasinating a high up figure.

Iron Chef Tamriel. Tonight we're doing something slightly different - we have TWO secret ingredients: Jarrin Root and Betrayal!