draw your stem line on your work. cut bias strips 1 1/2" wide from your stem fabric. fold the stem fabric in half -wrong sides together (like binding) and press. pin your raw edges down your drawn guideline. Sew 1/4 " from the raw edge. Fold the folded edge over your sewing line. Either hand or machine sew your folded edge.
Now, please test this first and adjust your cut width according to how it will work best for you. I am explaining this from memory and it's been a while since I did this. This is how I saw Eleanor Burns do it on TV one time.