I made ten samples for a tree branch and the final choice is between #2, #3, and #4.
For anyone interested in the methods employed:
#1 Soft cord wrapped with a scrap of furnishing fabric and stab stitched to the calico background.
#2 Soft cord wrapped with crinkly dyed muslin and stab stitched to the calico background.
#3 Couched lengths of knobbly yarn with scraps of green crinkly dyed muslin applied to suggest moss.
#4 Portuguese knotted stem stitch in various sizes with three strands of Anchor tapestry wool stitched onto onion netting and then applied as a slip.
#5 Soft random-dyed yarn stitched as a raised stem stitch band.
#6 As #1 but with different fabric.
#7 Silk scarf scrap wound around polyester toy filling and stab stitched to the calico. Moss as in #3.
#8 Same yarn as #5, various stitches with over-stitching also to suggest roundness.
#9 Wire inserted into a cotton rope and overcast with Anchor tapestry wool.
#10 Rope as #9 with different sized straight stitches close together.