The attached picture shows just how well nature adapts to what humans throw at it. I've seen many of these spruce trees growing in these railroad ties. A lot of miles of Maine's ATV and snowmobile trails are built on former railroad track beds, and in a lot of cases the rails were removed completely but the wooden ties were simply moved off the track bed and left there for nature to reclaim them. Over time spruce trees have seeded themselves in cracks through the ties like the little spruce in the picture. Eventually the railroad tie will completely rot and in it's place will be a beautiful spruce. I've often wondered with the amount of spruce trees we have in Maine, why we're called the Pine Tree State. :)