Thorn stitch

Thorn stitch is a decorative form of couching where a long thread is held down by an off-centred cross. It is often used to depict thorny stems or ferns, hence its name. Any type of embroidery thread can be used to work this stitch: both couched and couching elements can be worked with a single thread or you could use a different type/colour of thread for the pairs of crossing stitches.
N.B. this is a different version of thorn stitch from Thorn stitch (Mountmellick).
Method
Bring the needle up and work a long straight stitch. Then bring the needle up near the end of the first long stitch.
Work a pair of diagonal stitches so that they cross over the first long stitch.
Bring the needle up again to begin the next diagonal stitch.
Work a diagonal stitch, crossing over the first long stitch.
continue working pairs of diagonal stitches as required.
The pairs of diagonal stitches create the ‘thorns’ at each side of the long stitch.

Common uses
Embroidery Techniques
Related Stitches
References
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Mary Thomas’s Dictionary of Embroidery Stitches (1934) , p.198
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Jennifer Campbell, Ann-Marie Bakewell, Guide to Embroidery Stitches (2004) , p.108
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Sarah Whittle, The Needlecraft Stitch Directory (2012) , p.107