Here is how it works with my approach using negative painting techniques
When it comes to negative paintings I always start with the objects that are closest to me and work back.
Next time you paint a landscape, try starting with the foreground, then build the middle-ground and finish in the distance (background). Another way of describing it would be; work from the bottom to the top. This painting is a watercolour but the same approach works well for other painting media too.
I've made a diagram to show you the order of layers
The grasses were painted first, then the darks were laid down in the area I wanted to develop as trees. The cool blue grey established the outer edge of the trees and trunks (captured negative shapes). The final application of colour blocked in the sky. Remember that with negative painting you don't paint the object (i.e. the tree) - you paint around it!
Did you figure it out?
By the way, in case you were wondering, the blues and greys were made with Holbein Grey of Grey. It is wonderfully opaque and just like painting with velvet!
Paper: Strathmore Gemini 140lb CP
Holbein Watercolour: Burnt Siennna, Raw Sienna, Cerulean Blue, Shadow Green, Grey of Grey
Brushes: Cheap Joes 1" Skipper, Holbein Gold #12 round, Low-Cornell flat 3/4" 7750