This site has some ideas on increasing the humidity:

http://www.rcreptiles.com/blog/index...idity_problems

As to using hemlock, I wouldn't advise it. Certain trees, pine and cedar especially, secrete oils that can kill your snake(s) or at the very least make them seriously ill. Certain species of hemlock are also poisonous, so depending on what type/species of hemlock it was, that might be baaaaaaaaaaad news.

There's no hard and fast rule for what will work every time, as a lot of the equation depends on your setup and what your heat sources are. I had ceramic heat emitters on my tanks for a short time along with the UTH's and while they kept the temperatures up nicely, they destroyed the humidity.

There are a lot of people on here with way more knowledge than me that might hit in and offer some tips; you're in the right place to get an answer to your questions, so good luck!