What's your Mushroom Factor?

Those of you who’ve ever taken up a home renovation project are probably familiar with the “mushroom factor” – you decide to fix that leaky faucet, then you discover that the leak has been going on so long that the counter has rotted out beneath it and the floor is getting kind of mushy. So you start tearing that out and you see that the genius who put the sink in decided that it was okay to cut a huge hole in a support beam to run the pipe through and now oops—the beam’s starting to crack. So you open up a little more and—oh, my God!—the mice have gotten in and are chewing your electrical wires and your house is a bonfire just waiting to happen….

Well, I’ve realized that the same thing seems to be happening with my research on the historical novel I’m working on. The last one wasn’t too mushroomy, because it developed around information I’d already gathered during the course of working at Old Sturbridge Village. But for this one, I had to send my characters on a road trip, so now I’ve got to find out about: transportation, inns and taverns, every person/business they encounter along the way (with, of course, period-appropriate names, occupations, tools, clothes, etc., etc.). Plus I have to pick out a route for them and find out about the towns along the route. Then one of my characters decided to work on the railroad, another stubbornly insists on taking up with a prostitute (I told him this was a YA book, and he said “Well, that would be the ‘adult’ part, wouldn’t it?"), a third is getting embroiled in a child custody dispute, and somehow a circus with a conjuror, jugglers, singers, and six dancing ponies have been thrown into the mix. Whew! I can see myself researching this until doomsday and never getting all the details I’ll need to make it right!

So my question for you writers out there is—does your writing have a “mushroom factor,” too? What is it and how do you handle it?