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Gwen Marston taught us to take a bias strip 3 times wider than stem. Fold in thirds and with the raw edges underneath sew where you want it by sewing a basting stitch in the middle of the strip. Then finish the edges anyway you want and the basting thread is easy to take out.
The way I do stems/vines are to cut a 1" strip of material. Take to the ironing board, spray water on about 10" inches of the strip, fold in half , iron the wetted area and continue down the length of the strip. Then spray water gain on the fold strip and fold again not quit half and iron again, do this the length of the strip. This is how I made the vines, stems in the picture of the Rose of Sharon on my aviatar. Hope this helps you. Good luck.