The hem rolls up at the edge
Short answer: Single jersey always curls at a free edge. That is the nature of the fabric, not a flaw, and steaming or an extra stitch keeps the edge flat.
Why jersey curls
In single jersey the two sides of the fabric are knitted differently, so the right side and the wrong side behave separately. The tension in the fabric is therefore uneven, and a free edge always curls toward one side. The bottom edge usually curls upward, while vertical edges curl toward the back of the garment.
What the manufacturer can do
An edge can be secured with a folded hem and double stitching, a ribbed finish, or a tape on the inside of the fabric. That costs extra fabric and sewing time, which is why curling edges show up most in the thinnest and lightest garments. See bamboo tops for women.
Getting the edge to lie flat
Steam the edge and lay it flat under light pressure while it cools on a table or ironing board. That usually holds for a day or two before the fabric drifts back toward its natural shape. For a lasting fix, a tailor can stitch a thin hem along the edge instead.
Never cut the edge off
If you cut the edge off to remove the curl, the new edge curls too, since the problem sits in the knit structure itself, not in the specific thread. The real fix is always about securing the edge, not removing it and hoping for a different outcome.
When it is actually a flaw
If only one side of a garment curls, or the seam pulls crooked to one side, something is wrong with the stitching rather than the fabric itself. If all free edges curl roughly the same way all around, that is normal jersey behavior, not a production defect to complain about.
Does interlock curl too
Interlock is knitted the same way on both sides and therefore lies flat on its own without extra treatment. Knowing the difference lets you choose interlock over single jersey for garments where a flat edge matters most, such as tops and bamboo dresses with visible edges.
Does ironing help long term
Ironing only works briefly on a jersey edge, since the knit structure pulls it back toward its natural shape after a few hours of wear. Steam combined with light pressure while cooling holds a bit longer than plain ironing alone, but neither is a permanent fix. See bamboo t-shirt for women.
The edge changes over time
With many washes, jersey softens, and the curl often becomes somewhat less tight than on a brand new garment. Repeated washing at high heat, on the other hand, can weaken the elastane in the edge, making it curl less predictably. Wash according to the label to preserve the edge's behavior as well as possible.
Summary
A curling edge in single jersey is normal and comes from the knit structure, not the quality of the fabric. Steam and light pressure help temporarily, while a thin hem from a tailor gives a lasting fix. If only one side curls or the seam pulls crooked, that is a stitching flaw instead.
Frequently asked questions
Does interlock curl too?
No. Interlock is knitted the same way on both sides and therefore lies flat on its own, without the uneven tension that makes single jersey prone to curling.
Does ironing help against a curling edge?
Only briefly. Steam and light pressure while cooling hold a bit longer, but the edge soon returns to its natural curl once it warms back up.
Does it get worse over time?
A little, since the fabric softens with washing. The curl itself often becomes less tight, though, so overall it can feel less noticeable than when the garment was new.
You can find the full range at Bamboo-Clothing.com.
