Stockinette is probably the most instantly recognizeable knitted fabric. I remember when I finally learned to work stockinette after knitting lots of garter stitch. I looked down at those orderly little rows of Vs, and for the first time I thought “Hey, this is actually looking GOOD!”
Though it’s an extremely popular stitch pattern, stockinette stitch has a natural tendency to curl in on itself ( my swatch knit in Fuji, pictured above, is already curling! ). It doesn’t mean the knitter has done anything wrong – it’s just what stockinette does. Sometimes, this can be a design element. Overby’s neckband is just five rounds of stockinette left alone so it will roll, creating a nice casual effect. Brail, our stripey summer scarf, is worked entirely in stockinette, allowing it to roll in on itself and keep the wrong side of the fabric hidden.
If rolling is not desired, the most effective option for controlling it is to edge the stockinette with a stitch pattern that lies flat (like garter stitch or ribbing). The edging will need to be substantial enough to counteract the natural pull of the curling, so you’ll need more than just a couple of rows. Trial and error is the best way to determine how many rows of edging will be required to control the roll. Some yarns will curl less than others, since both construction and fiber content directly affect the amount of spring and bounce in a yarn. Your stitch gauge will also impact the amount of curling. If you knit very loosely on large needles, the fabric will curl less than if it’s knit tightly on small needles.
One final step that can control stockinette curling is blocking. Steaming or wet blocking your knitting can help relax the curl and flatten out the fabric. This can really help if you’re preparing to seam garment pieces worked in stockinette. The curling may not be completely eliminated, but blocking can loosen the rolling and make it easier for you to sew the seams.