I'd wait until Spring to plant the seedlings. You can start anytime to put the branches in water. I'll look for a reference to this. I remember doing this when I was in elementary school, so that's where I got the idea from. Especially since it's free . You can plant the branches in some soil, after they've developed a good set of roots and put them in pots, so they start to grow prior to spring over the winter months. Once the ground has thawed and you've had your last freeze of the year, I'd put them in the ground so they have all year to grow. In addition to that, the tall grass will be shorter, so your pine trees will have a good chance to get a jump start. I'll post more info about it once I find it. It's one of those things that's worked for me, and deer don't need a lot of cover to bed in(acreage), but you'll be able to concentrate them around you, and big bucks will also like bedding in this area, which will make your stand location closest to this place a gold mine come rut time. If there aren't any newer growths on the pine trees around you, you might have to wait until they start to grow new shoots. Although, it is possible to make the woody stem work, just takes more patience and you need to talk to the plants, to motivate them! lol
Edit: Here is a link to everything you need to know. If you have any questions, I might be able to help you understand it better. Just let me know.