The Wilderness is a story written by Tsukizubon Saruko. It ran in Issue 31 at http://s2b2.livejournal.com/178949.html, and is mirrored at http://www.shousetsubangbang.com/mirror/the-wilderness/.
From http://paranoidmuch.livejournal.com/2639.html: "had made me nervous about the weeds growing in my backyard. A wonderfully insidious horror story underscores the difficulties of being in a long-term relationship, and what can happen after you've known someone so intimately for years."
From pinboard.in: "the one about a couple working through their relationship problems amid a botanical apocalypse"
This story was, shall we say, heavily inspired by the album Ghost by Radical Face, which I only just stumbled into this year (SOMEHOW) and fell violently in love with. It is, if you're not familiar with it, a concept album about the history of houses, and about hauntings, and the intersections between the two. I should, in particular, credit the fact that I actually lifted quite a few images and main concepts from the song "Haunted" (as will be fairly obvious if you are familiar with it, ha ha), but elements of the entire album have been informing the entire story throughout, especially also "Wrapped In Piano Strings" and "Sleepwalking." I hope that this will be understood to be the homage it was intended to be, rather than, well, a rip-off.
You can also buy the entire album from Amazon.com MP3, here. In fact, I'd strongly recommend doing so, and indeed I think the story is much improved by listening to it while reading. If you'd like to take a test-drive first, you can pretty much find all of the songs on youtube.
I know there's a lot about this story that's left ambiguous, and I hope that's not too frustrating for anybody. I know perfectly well what I think was happening, and there are some clues to that throughout, but at the same time, I don't want to make that the one and only right answer, either. You get out of it what you get out of it, I guess, and I would say most interpretations are equally valid.
I apologize for any and all liberties I have taken with plant life/geography/etc. of the Pacific Northwest of the U.S. Many thanks to this site for helping me know what I should be picturing (as the northwest is one of the few dwindling places in the U.S. to which I have never been), though any mistakes are mine and no one else's.
Also worth noting is the fact that the Dan Sperber citation in the book Jon is reading is real, and also an interesting book worth checking out if you're into that sort of thing.