If you aren't ready to spend the 200-300 dollars needed to buy an underquilt for your hammock that doesn't mean that you have to be a 3 season hammock camper. The key to 4 season hammock camping is understanding how you trap heat to stay warm. While having an underquilt makes this easier not all of us can afford to drop that kind of coin on a hobby.
I personally do not own an under quilt but did want to get one more hike in this year, and while the winter here in North Georgia has been relatively mild the nights still drop into the low 30's. In the mountains however the temperature will dip into the mid 20's. I gave this a good bit of thought before hiking out on the A.T Approach toward Springer Mountain. I did invite some friends to join me but they were all seemingly busy or smart, you can decide. So not only was I testing my methods of winter hammock camping, I was doing so alone and needed to make sure I wasn't going to spend a frigid night huddled over a camp fire.
I use an Osprey Volt 75 backpack as one of my packs, which allowed me to pack plenty of gear, and while my pack was heavier than normal it was worth it to ensure I would be warm. I doubled down on the sleeping bags, carrying my 32 deg. down sleeping bag and a synthetic bag. I brought my Hennessy Hammock Double Bubble Sleeping Pad, and I bought a box of hand and foot warmers that you would use when skiing.
And although the gear that you bring is very important, how you set up your hammock and tarp is more important. When sleeping in the mountains, unless you are on the backside of the mountain, you will experience an increased velocity of wind, especially in the winter. Remember winter windy, summer sunny. Your goal is to trap as much of that heat with some insulating and thermal mass. Wind will come through and strip that trapped heat right out.
To do this, I set my hammock up so that it was roughly 4-6 in. off the ground while laying in it. Just enough to keep me comfortable and to keep cool air from pooling beneath me. This meant that my rain fly was staked with the edges nearly touching the ground. The remaining few open inches were packed with fallen leaves as a wind break, and leaves were packed underneath my hammock for thermal mass.
Luckily my research payed off and I was able to sleep comfortably in the winter weather. I should mention the wind was relentless all night and because of my leaf wall I felt very little to no wind at all. I believe this was the key to my success.
If you have any comments or tips for me please share them below as I am eager to learn about your ideas. Get creative and get outdoors.
Update - March 2015
Since posting this article I have purchased an underquilt. And while I still believe you can stay warm without one my pack weight was just getting to heavy.