The final picture in the set of four is the poppy field.
The poppies are in different sizes of French knots (larger closer to the front, worked with more strands in the needle, fewer strands further back) to create the effect of perspective. They peek through the grass in shades of green that is paler further back (perspective, again).
There are trees (satin stitch, straight stitch and French knots) and a mountain (in a shiny rayon thread) in the distance.
The trunk and branches of the fir trees are worked after the greenery by threading variegated brown thread between the stitches so that the wood of the tree can be seen between the leaves. The entire picture is worked over net, with blue and white net showing through to represent the sky.