I made them using 6mm needles by casting on one stitch, knitting that one front and back and then increasing both of the outer stitches by one on every row. Once I'd got to 70 I decreased each end of each row by one until all the stitches were gone.
By the time I'd knit two green ones I knew what they were destined to be. I knit two purple ones and joined them together to make a baby blanket.I then edged it in 2 rows of purple single crochet. I'm very happy with the result.