I was quite amazed to find out that not everyone creates their bias stems the same. A friend requested that I post a tutorial on how I do mine - so here it is. Now, this is not something I invented... just a technique that I've picked up along the way (as you do).
Step One: cut strips on the bias a bit longer than the length you require. For a 1/4" stem, you will need a 1" strip. Fold strip in half and press with raw edges together.
Step Two: pin strips onto your background, easing in fullness as required to achieve the desired curve. This is not the final placement of the stems, as they will be flipped over the stitching line.
Step Three: stitch quite close to the raw edges - about 1/8" - along the length of the stem.
Step Four: flip the stem over the stitching line into it's final placement. Pin in place.
I added smaller stems into this longer stem - unpick small sections and slip the small stem under, attach per the large stem, then restitch the large stem down.
Step Five: using your usual needleturn applique stitch, sew the folded edge onto the background.
Voila - your stem is sewn. From small stems gardens and bouquets grow...