Fabric cut on the bias has more stretch or "give" making bias-cut skirts and dresses particularly flattering, but folding up the fabric along the curve of the hemline is a challenge. The hems in round tablecloths and curved ruffles present the same challenge. There are several alternatives to making a traditional double-fold hem along a curve.
Using Hem Tape
It is difficult to iron up one fold on a curved edge. It is more difficult to iron up two. Making two folds along a curved hem requires adding many bulky tucks, which make the hem thick, stiff and unattractive. Finish the top edge of your hem with stretch lace or hem tape to avoid these problems. Both products stretch to allow you to sew curves without extra bulk. Hem tape and stretch lace are both available in packages in the notions departments of fabric stores. Cut your project to allow for a 3/8-inch hem. Sew 1/2-inch tape or lace to the right side of the hem by overlapping the edges 1/4 inch and sewing a straight seam down the middle of the overlap. Stretch tape or lace slightly as you sew. Use a seam gauge to iron up a 5/8-inch hem; include the tape in this measurement. Sew the hem in place by hand or with the blind hem stitch on your sewing machine.
Sew a curved hem in lightweight fabric, using a rolled hem foot on your sewing machine. If your machine does not have a rolled hem foot, you can usually purchase one from a sewing machine store. Cut your project with a 1/4-inch allowance for the hem. Set your machine to stitch a rolled hem according to the instructions. If your machine does not have a rolled hem stitch, you will probably be instructed to use a narrow zigzag stitch. A bamboo skewer is helpful for inserting the fabric into the foot. You may need to sew two small straight stitches at the beginning of the hem to hold the first section of the hem in place.
Overcasting the Edge
For an easy hem, cut your project with no allowance for the hem and finish the curved edge with an overcast stitch. A serger produces the best overcast hem, but you can also use a wide zigzag stitch with a very short stitch length. The stitching should be close enough so that no fabric shows between the stitches. Use thread that matches your fabric if you wish the hem to blend in or choose a contrasting colour of thread to make the hem into a decorative detail.
Finishing the Edge with Trim
Sew on trim to finish the edge without having to hem it. You can encase the edge in double-fold bias tape or just sew ornamental trim along the edge. For a finished look on the inside of the project, you may want to hem the garment with an overcast stitch or hem tape before you sew on ornamental trim.