Great for vines, rope effect, or flower stems, stem stitch is the perfect solution to single lines that curve. The nature of the stitch means it follows bends really nicely - just maybe take your stitches a little smaller as you go around tight curves.
Here's how ya do it!
Bring your needle up at point A and back down at B, making one straight stitch (photo one).
Bring your needle up at point C, which is in the middle above your first stitch (photo two).
Bring your needle back down at point D, which is in line with the end of your first stitch, about a half-stitch away (photo three).
Bring your needle up again at E, which is in the middle above your second stitch (photo four).
Go back down at F, which is in line with the end of your second stitch, about a half-stitch away (photo five).
Repeat as necessary.
TIP: Stem stitch is great for following curved lines, just follow the curve making sure the when you go back down at the end of each stitch you are on the line.
TIP: Make sure your stem stitches always start above the last stitch.