Sometimes, borders just flip me out.
See this? The edge of an otherwise beautifully knit sweater stubbornly insists on flipping out.
I've had this problem more times than I can count. It usually happens with bouncy yarn knit at a fairly firm tension. Single ply yarns seem to be the worst offenders. The very worst offender I had, though, was this baby sweater out of superwash in a slip-stitch pattern with a garter stitch border.
What is really happening here is that the stockinette is exhibiting its tendency to curl and the ribbing is just along for the ride. So changing to garter or seed stitch won't fix the problem, because it's the stockinette causing the problem and not the edge stitch. Slip-stitch patterns have an even more pronounced tendency to curl, and that's what made the baby sweater such a problem.
Ideas that sometimes help:
- Reduce the size of the needles for the border. Going down two sizes usually helps a lot, unless the garment was knit at a very tight tension. In my experience, the hems of tightly-knit garments just tend to roll.
- Reduce the number of stitches 5-20% on the first row of the border.
- Knit a row of purl before beginning the border. This will encourage the border to roll towards the body instead of away from it. This is a weak remedy, but it's fixed some borderline cases for me.
- Increase the depth of the border. Sometimes, the garment gauge distorts the border gauge, and the border needs an extra inch or so to settle into shape.
If the border draws in narrower than the main body of the sweater, it will cling to the body and help keep the border in place. A nice deep border worked on needles several sizes smaller and up to 20% fewer stitches can help dramatically, particularly if you toss in a purl row before the border.
The tendency of stockinette to flip up is so pronounced that you can use a single row of purl stitches anywhere in any knit piece to make a crisp fold line. I do this anywhere I want the fabric to fold back on itself (hems, turn-back cuffs, etc). You can also use a single row of purl right before starting a border to encourage the border to turn towards the body instead of flipping away from it. (This doesn't work with garter stitch borders, though.)
Ribbing used as a border at the cuffs or body of the sweater really needs to be about 3" deep. It takes about 6 rows (1" or so in most handknit gauges) for ribbing to establish itself and really draw in. So during the first inch of transition from stockinette, the ribbing isn't really free to assert itself, and in the last inch in the transition to the air, the ribbing is a bit insecure. So give it enough depth so it can really be ribbing.
My personal experience is that ribbing is a great finish for men's and children's sweaters, but it often doesn't work so well on women. We have hips, and the flare of the hip encourages borders to misbehave. For women's sweaters, I use different kinds of edge treatments to tame the stockinette curl.
One of my favourites is a turned knit hem. Make the sweater as long as you want it, purl one row, and then knit at least another inch and a half. Gently tack the live stitches down to the wrong side of the sweater, making sure to allow enough give in your stitching for the sweater to stretch any way it wants to. The resulting edge is crisp, tailored, and unobtrusive. This will always counteract the flip if the hem is deep enough and you sew it down loosely.
A lace edging often works beautifully, particularly one with an undulating edge. Typically, I start working these just below the waist because the more beautiful ones are 4-6" long when worked at a worsted gauge. I've worked these top-down, but often choose to work the edging bottom-up and then graft it in place. Sideways lace edgings work as well.
Lining or facing the sweater can help with slightly misbehaving edges. You see this a lot in vintage knits, edges that are tamed by sewing in a lining or facing. A wide grosgrain ribbon can help stabilize a button band or horizontal edge. I've used this to good effect in children's sweaters, but I don't think a ribbon would have enough oomph to stabilize the body border in an adult sweater. You'd need a deep facing to make an adult border behave, and in the process, you would compromise the elasticity of the edge. This is a good solution for some garments, but you rarely see it in modern knits.