These are examples of Needle Lace.
I learned this technique from Susan Brittingham at Quilt University (online).
Use a heavy water-soluble stabilizer in a spring-tension embroidery hoop (These are thinner than the old wooden ones, and will fit under the foot of your machine.) along with some tulle or netting. Then you sew-sew-sew ... After the stabilizer is washed away, the netting gives the piece some body and structure which may be needed for larger pieces like the leaf and the tree canopy. The moss seems to get thick enough that it manages to support itself after the stabilizer washes away.
When your free-standing embroidery is complete, it can be appliqued to a quilt or wall-hanging.
The background fabric is a hand-dyed scrunch & dump that I did in one of Marjie McWilliams dying classes also at Quilt University.