Kitchener/Mattress Stitch Confusion

I’ve created a blue scarf that is a bit too narrow, so I would like to add a stripe of white on either side. The finished product would look something like this:

How do I best attach my side pieces – using a kitchener or mattress stitch or something else?

I know I could just frog it and start over, but I need to know how to do seams anyway at some point. I might as well learn now. :smiley:

Thanks,
Lisa

Mattress stitch would work fine, but to be honest, I think you’d be better severed just picking up and knitting the stitches.

Along the edge, you will pick up about 2 stitches for ever 3 rows of stitches. (I’m asuming you are going to work garter stitch up the side. You may need to adjust a little, and I’d suggest swatching to see what your stitch to row ratio is)
Here’s a video on how to pickup and knit stitches along an edge
http://knittinghelp.com/knitting/videos/adv-tech/pu-along-side-edge.mpg

This will be far less work than knitting and sewing together.