Knit elastic

I have seen knitted elastic. I thought “If I knit on the bias it will be very stretchy.”

Well for stockinette that is true but for garter stitch it is more stretchy on the grainline. Why is that and if I do want to knit a strand of elastic would garter stitch be the best choice since elastic is usually there for horizontal stretch?

Garter stitch uses up more yarn and is stretchier than stockinette in the vertical direction (from one row to the next row).
Are you planning on knitting on the bias? What are you going to make?

I think that knitting a strand of elastic would be good for knitting skirts where you want that stretch since adding a zipper would be too hard, at least for me.

So to prevent unraveling and still have that stretch the easiest thing to do is to knit a hem, knit a strand of elastic, and sew the hem by hand.

This is where I was thinking about knitting on the bias to get that stretch.