I went to Italy last October and picked up 2 pine nuts that had found on the ground. I crushed the shell of one with a large stone and ate the nut inside and put the other one in my pocket. When I got home, I decided to try and grow a pine tree so I placed the whole shell in the freezer for a few days (one week maybe) to make the seed “believe” it was winter. Then, I took it out of the freezer and loosely wrapped the shell inside some very wet cotton wool, pouring water on it regularly to ensure it never dried. After a couple of weeks, the shell started to split.
A couple of days later, a green root came out.
I gently picked up the new seedling being careful not to damage the root and placed it in a small pot of compost before the root got stuck inside the cotton wool. Six weeks later (14th December), the first leave had come out. I now have my own pine tree!
Post updated 25/06/2015. 6 months on, the seedling is making side shoots.
To prevent the pine tree from growing too large, I will keep it inside a pot.